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The public health crisis created by the COVID-19 pandemic has spurred a deluge of scientific research aimed at informing the public health and medical response to the pandemic. However, early in the pandemic, those working in frontline public health and clinical care had insufficient time to parse the rapidly evolving evidence and use it for decision-making. Academics in public health and medicine were well-placed to translate the evidence for use by frontline clinicians and public health practitioners. The Novel Coronavirus Research Compendium (NCRC), a group of >60 faculty and trainees across the United States, formed in March 2020 with the goal to quickly triage and review the large volume of preprints and peer-reviewed publications on SARS-CoV-2 and COVID-19 and summarize the most important, novel evidence to inform pandemic response. From April 6 through December 31, 2020, NCRC teams screened 54 192 peer-reviewed articles and preprints, of which 527 were selected for review and uploaded to the NCRC website for public consumption. Most articles were peer-reviewed publications (n = 395, 75.0%), published in 102 journals; 25.1% (n = 132) of articles reviewed were preprints. The NCRC is a successful model of how academics translate scientific knowledge for practitioners and help build capacity for this work among students. This approach could be used for health problems beyond COVID-19, but the effort is resource intensive and may not be sustainable in the long term.

The coronavirus disease 2019 (COVID-19) pandemic thrust the field of public health into the spotlight. For many epidemiologists, biostatisticians, and other public health professionals, this caused the professional aspects of our lives to collide with the personal, as friends and family reached out with concerns and questions. Learning how to navigate this space was new for many of us and required refining our communication style depending on context, setting, and audience. Some of us took to social media, utilizing our existing personal accounts to share information after sorting through and summarizing the rapidly emerging literature to keep loved ones safe. However, those in our lives sometimes asked unanswerable questions, or began distancing themselves when we suggested more stringent guidance than they had hoped for, causing additional stress during an already traumatic time. We often had to remind ourselves that we were also individuals experiencing this pandemic and that our time-intensive efforts were meaningful, relevant, and impactful. As this pandemic and other public health crises continue, we encourage members of our discipline to consider how we can best use shared lessons from this period and to recognize that our professional knowledge, when used in our personal lives, can promote, protect, and bolster confidence in public health.

Background: Mobility is an important risk determinant for HIV given the potential for intermittent access to HIV services. Mobility may be particularly relevant among female sex workers, (FSW) who have been shown to be at high risk for HIV in settings around the world. Data regarding the role mobility plays in exacerbating HIV risks among FSW across Sub-Saharan Africa remains limited, and data on FSW in Guinea-Bissau is sparse.Methods: FSW in four regions of Guinea-Bissau were recruited with a respondent-driven sampling (RDS) method and participated in an integrated bio-behavioral survey. Associations between reported mobility and social and HIV vulnerabilities among FSW in Guinea-Bissau were assessed using multivariable logistic regression models. Results: 34.8% of respondents reported mobility to one location and 15.7% reported mobility to more than one location within the past six months. Statistical analysis demonstrated that mobility to more than one destination was significantly associated with recent sex without a condom with both clients (aOR: 2.57 (95% CI: 1.10, 6.00)) and non-paying partners (aOR: 4.73 (95% CI: 2.24, 10.02)) compared to non-mobility. However, mobility to one or more locations was also associated with higher odds of receiving HIV prevention information (mobility to one location: aOR: 1.63 (95% CI: 1.07, 2.49); mobility to >1 location: aOR: 2.34 (95% CI: 1.28,4.26)) and mobility to more than one location was associated with more engagement with HIV-related organizations (aOR: 2.26 (95% CI: 1.27, 4.04)).Conclusions: These results suggest that while some prevention services including HIV prevention information reach mobile FSW in Guinea-Bissau, HIV prevention needs remain unmet for mobile FSW in Guinea-Bissau.

Purpose of Review eHealth tools are increasingly utilized for communication with patients. Although efficacious and cost-effective, these tools face several barriers that challenge their ethical use in sexual health. We reviewed literature from the past decade to pick illustrative studies of eHealth tools that deliver results of laboratory tests for sexually transmitted infections, including the human immunodeficiency virus, as well as partner notifications. We describe ethical implications for such technologies. Recent Findings Our review found that despite widespread research on the use of eHealth tools in delivering laboratory results and partner notifications, these studies rarely measured or reported on the ethical implications. Such implications can be organized according to the four major principles in bioethics: beneficence, patient autonomy, non-maleficence, and justice. The beneficence of eHealth typically measures efficacy in comparison to existing standards of care. Patient autonomy includes the ability to opt in or out of eHealth tools, right-based principles of consent, and sovereignty over healthcare data. To adhere to the principle of non-maleficence, relevant harms must be identified and measured—such as unintentional disclosure of illness, sexual orientation, or sexual activity. Justice must also be considered to accommodate all users equally, irrespective of their literacy level, with easy-to-use platforms that provide clear messages. Summary Based on case studies from this review, we developed a list of recommendations for the ethical development and evaluation of eHealth platforms to deliver STI/HIV results to patients and notifications to partners.

Increasing diverse engagement in the Society for Epidemiologic Research (SER) will positively impact the field of epidemiology. As the largest and longest-running epidemiologic society in North America, SER has long been a pioneer in promoting diversity and inclusion. A recent survey of SER members, however, showed there is still room for improving diversity, inclusion, representation, and participation in the Society. In this commentary, as members of both the SER and the Johns Hopkins Bloomberg School of Public Health Department of Epidemiology’s Inclusion, Diversity, Equity, Anti-Racism, and Science (Epi IDEAS) Working Group, we recommend 4 goals for the SER Annual Meeting and beyond: 1) convene epidemiologic researchers with diverse backgrounds and ideas; 2) promote an inclusive environment at the SER Annual Meeting; 3) develop, compile, and disseminate best practices to honor diversity in epidemiologic research; and 4) increase prioritization of health disparities research and methods. We also suggest strategies for achieving these goals so that SER can better include, support, and elevate members from historically disadvantaged groups. While our recommendations are tailored specifically to SER, the greater epidemiologic and academic communities could benefit from adopting these goals and strategies within their professional societies and conferences.

IntroductionAssessing the impact of COVID-19 policy is critical for informing future policies. However, there are concerns about the overall strength of COVID-19 impact evaluation studies given the circumstances for evaluation and concerns about the publication environment. This study systematically reviewed the strength of evidence in the published COVID-19 policy impact evaluation literature.MethodsWe included studies that were primarily designed to estimate the quantitative impact of one or more implemented COVID-19 policies on direct SARS-CoV-2 and COVID-19 outcomes. After searching PubMed for peer-reviewed articles published on November 26, 2020 or earlier and screening, all studies were reviewed by three reviewers first independently and then to consensus. The review tool was based on previously developed and released review guidance for COVID-19 policy impact evaluation, assessing what impact evaluation method was used, graphical display of outcomes data, functional form for the outcomes, timing between policy and impact, concurrent changes to the outcomes, and an overall rating.ResultsAfter 102 articles were identified as potentially meeting inclusion criteria, we identified 36 published articles that evaluated the quantitative impact of COVID-19 policies on direct COVID-19 outcomes. The majority (n=23/36) of studies in our sample examined the impact of stay-at-home requirements. Nine studies were set aside because the study design was considered inappropriate for COVID-19 policy impact evaluation (n=8 pre/post; n=1 cross-section), and 27 articles were given a full consensus assessment. 20/27 met criteria for graphical display of data, 5/27 for functional form, 19/27 for timing between policy implementation and impact, and only 3/27 for concurrent changes to the outcomes. Only 1/27 studies passed all of the above checks, and 4/27 were rated as overall appropriate. Including the 9 studies set aside, reviewers found that only four of the 36 identified published and peer-reviewed health policy impact evaluation studies passed a set of key design checks for identifying the causal impact of policies on COVID-19 outcomes.DiscussionThe reviewed literature directly evaluating the impact of COVID-19 policies largely failed to meet key design criteria for inference of sufficient rigor to be actionable by policy-makers. This was largely driven by the circumstances under which policies were passed making it difficult to attribute changes in COVID-19 outcomes to particular policies. More reliable evidence review is needed to both identify and produce policy-actionable evidence, alongside the recognition that actionable evidence is often unlikely to be feasible.

Background HIV services, like many medical services, have been disrupted by the COVID-19 pandemic. However, there are limited data on the impacts of the COVID-19 pandemic on HIV treatment engagement outcomes among transgender (trans) and nonbinary people. This study addresses a pressing knowledge gap and is important in its global scope, its use of technology for recruitment, and focus on transgender people living with HIV. The objective of this study is to examine correlates of HIV infection and HIV treatment engagement outcomes (i.e., currently on ART, having an HIV provider, having access to HIV treatment without burden, and remote refills) since the COVID-19 pandemic began. Methods We utilized observational data from the Global COVID-19 Disparities Survey 2020, an online study that globally sampled trans and nonbinary people (n = 902) between April and August 2020. We conducted a series of multivariable logistic regressions with lasso selection to explore correlates of HIV treatment engagement outcomes in the context of COVID-19. Results Of the 120 (13.3%) trans and nonbinary people living with HIV in this survey, the majority (85.8%) were currently on HIV treatment. A smaller proportion (69.2%) reported having access to an HIV provider since COVID-19 control measures were implemented. Less than half reported being able to access treatment without burdens related to COVID-19 (48.3%) and having the ability to remotely refill HIV prescription (44.2%). After adjusting for gender in the multivariable models, younger age and anticipated job loss were significantly associated with not having access to HIV treatment without burden. Outcomes also significantly varied by geographic region, with respondents reporting less access to an HIV provider in nearly every region outside of South-East Asia. Conclusion Our results suggest that currently taking ART, having access to an HIV provider, and being able to access HIV treatment without burden and remotely refill HIV medication are suboptimal among trans and nonbinary people living with HIV across the world. Strengthening support for HIV programs that are well-connected to trans and nonbinary communities, increasing remote access to HIV providers and prescription refills, and providing socioeconomic support could significantly improve HIV engagement in trans and nonbinary communities.

The public health crisis created by the SARS-CoV-2 pandemic has spurred a deluge of scientific research aimed at informing public health and medical response to the COVID-19 pandemic. However, those working in frontline public health and clinical care had insufficient time to parse the rapidly evolving evidence and use it for decision making. Academics in public health and medicine were well-placed to translate the evidence for use by frontline clinicians and public health practitioners. The Novel Coronavirus Research Compendium (NCRC), a group of >50 faculty and trainees, began in March 2020 with the goal to quickly triage and review the large volume of preprints and peer-reviewed publications on SARS-CoV-2 and COVID-19, and to summarize the most important, novel evidence to inform pandemic response. From April 6, 2020 through January 1, 2021, 54,192 papers and preprints were screened by NCRC teams and 527 were selected for review and uploaded to the NCRC website for public consumption. The majority of papers reviewed were peer-reviewed publications (n=395, 75%), published in 102 journals; 25% (n=132) of papers reviewed were of preprints. The NCRC is a successful model of how academics can support practitioners by translating scientific knowledge into action and help to build capacity among students for this work. This approach could be used for health problems beyond COVID-19, but the effort is resource intensive and may not be sustainable over the long term.

Background The coronavirus pandemic has necessitated a range of population-based measures to stem the spread of infection. These measures may be associated with disruptions to other health services including for gay, bisexual, and other men who have sex with men (MSM) at risk for or living with HIV. Here, we assess the relationship between stringency of COVID-19 control measures and interruptions to HIV prevention and treatment services for MSM. Setting Data for this study were collected between April 16, 2020, and May 24, 2020, as part of a COVID-19 Disparities Survey implemented by the gay social networking app, Hornet. Pandemic control measures were quantified using the Oxford Government Response Tracker Stringency Index: each country received a score (0-100) based on the number and strictness of 9 indicators related to restrictions, closures, and travel bans. Methods We used a multilevel mixed-effects generalized linear model with Poisson distribution to assess the association between stringency of pandemic control measures and access to HIV services. Results A total of 10,654 MSM across 20 countries were included. Thirty-eight percent (3992/10,396) reported perceived interruptions to in-person testing, 55% (5178/9335) interruptions to HIV self-testing, 56% (5171/9173) interruptions to pre-exposure prophylaxis, and 10% (990/9542) interruptions to condom access. For every 10-point increase in stringency, there was a 3% reduction in the prevalence of perceived access to in-person testing (aPR: 0·97, 95% CI: [0·96 to 0·98]), a 6% reduction in access to self-testing (aPR: 0·94, 95% CI: [0·93 to 0·95]), and a 5% reduction in access to pre-exposure prophylaxis (aPR: 0·95, 95% CI: [0·95 to 0·97]). Among those living with HIV, 20% (218/1105) were unable to access their provider; 65% (820/1254) reported being unable to refill their treatment prescription remotely. Conclusions More stringent responses were associated with decreased perceived access to services. These results support the need for increasing emphasis on innovative strategies in HIV-related diagnostic, prevention, and treatment services to minimize service interruptions during this and potential future waves of COVID-19 for gay men and other MSM at risk for HIV acquisition and transmission.

BackgroundGlobally, the coronavirus pandemic has necessitated a range of population-based measures in order to stem the spread of infection and reduce COVID-19-related morbidity and mortality. These measures may be associated with disruptions to other health services including for gay, bisexual, and other men who have sex with men (MSM) at risk for or living with HIV. Here, we assess the relationship between stringency of COVID-19 mitigation strategies and interruptions to HIV prevention and treatment services for MSM.MethodsData for this study were collected as part of a COVID-19 Disparities Survey implemented by the gay social networking app Hornet, with data collected between April 16th, 2020 and May 24th, 2020. Data were assessed for countries where at least 50 participants completed the survey, to best evaluate country-level heterogeneity. We used a modified Poisson regression model, with clustering at the country-level, to assess the association between stringency of pandemic control measures and access to HIV services. Pandemic control measures were quantified using the Oxford Government Response Tracker Stringency Index; each country received a score (0-100) based on the number and strictness of nine indicators related to school and workplace closures and travel bans.ResultsA total of 10,654 MSM across 20 countries were included in these analyses. The mean age was 34.2 (standard deviation: 10.8), and 12% (1264/10540) of participants reported living with HIV. The median stringency score was 82.31 (Range:[19.44, Belarus]-[92.59, Ukraine]). For every ten-point increase in stringency, there was a 3% reduction in the prevalence of access to in-person testing (aPR: 0.97, 95% Cl:[0.96, 0.98]), a 6% reduction in the prevalence of access to self-testing (aPR: 0.94, 95% Cl:[0.93, 0.95]), and a 5% reduction in access to PrEP (aPR: 0.95, 95% Cl:[0.95, 0.97]). Among those living with HIV, close to one in five (n = 218/1105) participants reported being unable to access their provider either in-person or via telemedicine during the COVID-19 pandemic, with a greater proportion of interruptions to treatment services reported in Belarus and Mexico. Almost half (n = 820/1254) reported being unable to refill their HIV medicine prescription remotely.ConclusionsMore stringent government responses were associated with decreased access to HIV diagnostic, prevention, and treatment services. To minimize increases in HIV-related morbidity and mortality, innovative strategies are needed to facilitate minimize service interruptions to MSM communities during this and potential future waves of COVID-19.

South Africa processes 5.1 million HIV CD4, viral load (VL), and tuberculosis (TB) tests annually. This pilot non-randomized trial in South Africa explored an intervention (“MatlaMobile”) to deliver laboratory results via mobile phone. Adults completing CD4, VL, and/or TB laboratory tests were enrolled—either receiving results by returning to clinic (control, n = 174) or mobile phone (intervention, n = 226). Study staff instructed control participants to return within 6 days (standard-of-care). MatlaMobile instructed intervention participants with clinically actionable results requiring intervention or treatment change (i.e.

Background: An estimated 44–69% of female sex workers (FSW) in South Africa are living with HIV, among whom 39% are virally suppressed. Digital technologies—increasingly advanced and accessible to marginalized populations—present new opportunities to improve the HIV care continuum. The objective of this study was to explore potential facilitators and barriers to incorporating mobile phones and advanced technologies (e.g., biometric identification methods, mobile phone applications for social media and other uses, and chatbots) to deliver HIV-related interventions to cisgender FSW living with HIV in Durban, South Africa. Methods: Four semi-structured, focus group discussions (FGDs) were conducted with 22 cisgender FSWs in December 2018. Participants were recruited from the ongoing Siyaphambili trial using maximum variation sampling to optimize diversity in participant age and sex work venue. FGDs were audio recorded in isiZulu, and translated and transcribed into English. Transcripts were inductively coded using thematic analysis and sub-themes were iteratively refined to connect and evaluate the saliency of codes. Results: Phone ownership was motivated by a desire to remain safe and to connect with family, peers, and clients. When FSW did not have access to a mobile phone, they reported sharing phones with their peers, though sharing only occurred under specific conditions. Still, to integrate mobile phones into HIV care, FSW identified consistent access to mobile phones as a key barrier. Mobile phone turnover due to frequent selling of phones to meet other financial priorities, substance use, and theft were common. To integrate advanced technologies into HIV care, FSW identified convenience, security, and additional opportunities for social support as the main facilitators. For example, FSW described how biometric identification at clinics could eliminate the need to retain a clinic card. FSW also described how chatbots could easily set medication alarms or be available to assist in emergencies. Barriers for advanced technologies included maintaining privacy, potential threats to security, and cost. Conclusions: FSWs were receptive to digital technologies for HIV care and beyond, but they also described many barriers such as inconsistent phone ownership and threats to privacy. As phone ownership grows and HIV programs increasingly leverage digital tools, strong considerations are needed to ensure the most vulnerable are not systematically excluded.

Isoniazid preventive therapy (IPT) reduces the risk of active tuberculosis among people living with HIV, but implementation of IPT in South Africa and elsewhere remains slow. The objective of this study was to examine both nurse perceptions of clinical mentorship and patient perceptions of in-queue health education for promoting IPT uptake in Potchefstroom, South Africa. We measured adoption, fidelity, acceptability, and sustainability of the interventions using both quantitative and qualitative methods. Adoption, fidelity, and acceptability of the interventions were moderately high. However, nurses believed they could not sustain their increased prescriptions of IPT, and though many patients intended to ask nurses about IPT, few did. Most patients attributed their behavior to an imbalance of patient-provider power. National IPT guidelines should be unambiguous and easily implemented after minimal training on patient eligibility and appropriate medication durations, nurse-patient dynamics should empower the patient, and district-level support and monitoring should be implemented.

Purpose: Chest binding, or compressing the chest tissue, is a common practice among transmasculine individuals that can promote mental health, but frequently results in negative physical health symptoms. The purpose of this study was to assess the prevalence and correlates of care seeking for binding-related health concerns among transmasculine adults. Methods: Descriptive statistics were calculated and logistic regression models were run using data from the Binding Health Project, a cross-sectional online survey among transgender adults who had practiced chest binding (n=1800). The analysis was restricted to transmasculine individuals who had consistent access to health care and were female assigned at birth or intersex (n=1273). Results: Of 1273 participants, 88.9% had experienced at least one binding-related symptom and 82.3% believed that it was important to discuss chest binding with their health care provider, while 14.8% had sought care related to binding. Participants reporting pain, musculoskeletal, or neurological symptoms had 3.19, 1.85, and 1.72 times the adjusted odds, respectively, of seeking care compared to those who did not report those symptoms (95% confidence intervals [CIs]: 1.38–7.37; 1.12–3.06; 1.10–2.68). Care seeking was associated with feeling safe and comfortable initiating a conversation about binding with one's provider (adjusted odds ratio [AOR]=2.07, 95% CI 1.32–3.24). Care seeking was not significantly associated with feeling comfortable receiving a chest examination (AOR=1.07, 95% CI 0.71–1.62). Conclusion: Low rates of care seeking for binding-related symptoms may be driven by lack of access to a provider with whom patients feel safe and comfortable, rather than by general discomfort with chest examinations. While transmasculine patients may be most likely to present with musculoskeletal, neurological, or pain-related concerns, providers should also assess for other symptoms. Providers should be familiar with the benefits and potential complications of binding and initiate non-stigmatizing positive discussions about binding with their transmasculine patients.

Background Household surveys are an essential tool for vaccine coverage monitoring in developing countries, and the World Health Organization (WHO) Expanded Program on Immunization (EPI) cluster survey design has been a default choice for decades. In response to methodological limitations of the traditional EPI sampling, alternative methods have been proposed, based on modern statistical and geographical techniques. This study compared the coverage estimates and the time efficiency of the EPI sampling design and two alternative methods: the compact segment sampling and innovative grid-based geographical information system (GIS) sampling. Methods We conducted a series of equal-sized concurrent prospective vaccine coverage surveys in Karachi, Pakistan, from January to December 2016, using traditional EPI, compact segment and grid-based GIS sampling methods. Results No differences in vaccine coverage estimates were identified across sampling methods in the peri-urban setting; however, due to stronger clustering effects and correct incorporation of sampling weights, the compact segment [design effect (DEFF) = 2.03] and the grid-based GIS surveys (DEFF = 1.72) had higher design effects and, therefore, appeared to have lower statistical precision than the traditional EPI surveys (DEFF = 1.57). To achieve the same level of apparent precision, data collection activities in the compact segment surveys would require more than twice the implementation time needed compared with the traditional EPI surveys. Conclusions The precision of the EPI surveys appeared higher than that of the alternative methods because, under a questionable self-weighting assumption, the estimated design effect did not account for variable sampling weights. The compact segment and grid-based GIS methods were designed to improve randomness and representativeness of sampling households. Although these alternative methods did not result in coverage estimates that differed from the EPI survey results in the peri-urban setting, they have a lower risk of selection bias and therefore may be preferred.

In South Africa, high attrition rates throughout the care continuum present major barriers to controlling the HIV epidemic. Mobile health (mHealth) interventions may provide innovative opportunities for efficient healthcare delivery and improving retention in care. In this formative research, we interviewed 11 patients and 28 healthcare providers in North West Province, South Africa, to identify perceived benefits, concerns and suggestions for a future mHealth program to deliver HIV Viral Load and CD4 Count test results directly to patients via mobile phone. Thematic analysis found that reduced workload for providers, reduced wait times for patients, potential expanded uses and patient empowerment were the main perceived benefits of an mHealth program. Perceived concerns included privacy, disseminating distressing results through text messages and patients' inability to interpret results. Participants felt that an mHealth program should complement face-to-face interactions and educational information to interpret results is needed. Providers identified logistical considerations and suggested protocols be developed. An mHealth program to deliver HIV test results directly to patients could mitigate multiple barriers to care but needs to be tested for efficacy. Concerns identified by patients and providers must be addressed in designing the program to successfully integrate with health facility workflow and ensure its sustainability.

BackgroundWe characterised the impact of COVID-19 on the socioeconomic conditions, access to gender affirmation services and mental health outcomes in a sample of global transgender (trans) and non-binary populations.MethodsBetween 16 April 2020 and 3 August 2020, we conducted a cross-sectional survey with a global sample of trans and non-binary people (n=849) through an online social networking app. We conducted structural equational modelling procedures to determine direct, indirect and overall effects between poor mental health (ie, depression and anxiety) and latent variables across socioecological levels: social (ie, reduction in gender affirming services, socioeconomic loss impact) and environmental factors (ie, COVID-19 pandemic environment).ResultsAnxiety (45.82%) and depression (50.88%) in this sample were prevalent and directly linked to COVID-19 pandemic environment. Adjusted for gender identity, age, migrant status, region, education and level of socioeconomic status, our final model showed significant positive associations between relationships of (1) COVID-19 pandemic environment and socioeconomic loss impact (β=0.62, pConclusionThe study results supported the importance of bolstering access to gender affirming services and strengthening socioeconomic opportunities and programmatic support to buffer the impact of COVID-19 pandemic environment on poor mental health among trans and non-binary communities globally.

Porewater transport and diagenetic reactions strongly regulate the mobility of metals in sediments. We executed a series of laboratory experiments in Gust chamber mesocosms to study the effects of hydrodynamics and biogeochemical transformations on the mobility and speciation of Zn in contaminated sediments from Lake DePue, IL. X-ray absorption spectroscopy (XAS) indicated that the oxidation of surficial sediments promoted the formation of more mobile Zn species. Bulk chemical measurements of porewater, overlying water, and sediment also suggested that this process liberated aqueous metals to porewater and facilitated Zn efflux to the overlying water. In addition, sediment resuspension events increased the release of aqueous metals to both surficial porewater and the overlying water column. XAS analysis indicated that resuspension increased dissolution of Zn-sequestering mineral phases. These results show that both steady slow porewater transport and rapid episodic resuspension are important to the release of metal from fine-grained, low-permeability contaminated sediments. Thus, information on metals speciation and mobility under time-varying overlying flow conditions is essential to understanding the long-term behavior of metals in contaminated sediments.

The equipment described consists of a micro-camera, and a flash tube unit. The micro-camera embodies a single leaf electromagnetic shutter. The leaf is inclined, and the lower side is silvered to reflect the microscope eyepiece light cone Into a viewing eyepiece. The shutter is actuated by a separate foot-operated timer, giving exposures from I sec.-I 300 sec. The flash-tube is used in conjunction with the camera, to give an exposure of 5 micro-seconds. It has mercury electrodes and forms a light source 3 millimetres in diameter, of great intrinsic brilliance. Using an I ford 109 filter, 94°, of the light output, as recorded on Panatomic X film, lies within the wavelength range 5000°-6400 A. This is the corrected range for achromatic objectives. The tube operates at 950 volts D.C., and dissipates 4 joules. The light output is sufficient for 2 mm. oil immersion phase contrast and dark ground photographs.The photographic technique used by the author is described.

An optical system is described which can, for a number of applications, be used in place of the quartz rod method of trans-illuminating organs in an anaesthetized, intact animal for microscopical examination, and photography. It transmits approximately ten times more light than a quartz rod under the same conditions, and gives a conical illuminating beam, allowing considerably higher resolution. These factors permit photography of the organ in greater detail than is possible with the quartz rod technique. A specially designed microscope stage is used.The micro-camera embodies a reflecting single leaf electric shutter and is used in conjunction with a mercury-argon flash tube. The tube has a 3 mm. diameter light source rich in the yellow and green wavelengths, and gives an 8 joule flash of 10 micro-seconds duration. This freezes the motion of the circulating blood cells. This equipment is fully described in a previous paper.