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The characteristics of most viruses are best demonstrable by their effects on hosts. It is therefore desirable to determine the pathogenicity of a given virus for as many species of animals as possible. It seems to us of both practical and academic interest to find out the effect of various viruses upon the Chinese hamster, a species of rodent readily obtainable. In the present communication, the susceptibility of the Chinese hamster to fixed rabies virus is recorded.A strain of fixed rabies virus after 137 rabbit passages from a local street virus, was used. The brain virus preserved in 50% glycerin was thoroughly ground in a sterile mortar and suspended in saline solution. Normal Chinese hamsters weighing 20–30 gm. were divided into several groups and each group was separately inoculated with various dilutions of the rabbit brain virus through different routes. In intracerebral inoculation, the hamsters were anesthetized and 0.05 cc. of the ground virus suspension was injected through an opening in the skull posterior to the eye and lateral to the mid-dorsal line. In intraperitoneal, intratesticular, intramuscular and subcutaneous injections, 0.5 cc. of virus suspension was introduced each time. The latter 2 routes of injection were always made over the right thigh. Animals, after injection, were kept separately in cages and observed for over one month.After intracerebral inoculations, the infected animals began to show general weakness and tremor of different parts of the body in 5 to 8 days. This was followed by progressive unsteadiness of gait accompanied by weakness of the hind-legs, leading in 24 hours to definite paralysis. The upper limbs were found to be involved later. At the terminal stage all limbs became paralyzed, respiratory movements feeble and the skeletal muscles flabby.

It has been noted1that the Chinese hamster is susceptible to fixed rabies virus, but its susceptibility to street rabies virus still remains to be determined. Observations on its behavior to infection by a strain of street rabies virus are, therefore, described here.A fresh local strain of street rabies virus from dog was used in the present study. The original virus preserved in 50% glycerine was thoroughly ground in a sterile mortar and suspended in saline solution for inoculation. Chinese hamsters weighing 20-30 gm. were divided into several groups and each was separately inoculated with various dilutions of the dog brain virus through different routes as indicated in the table. The technique of inoculation was similar to that used previously.1The records of observations made on the incubation period, mortality, and days of death in relation to routes of inoculation and concentration of virus introduced are summarized in Table I.Ten to 20 days after inoculation with the virus, the infected animals began to show increased excitability, which became very pronounced within 24 hours after its first appearance. The animals generally ran about constantly and bit the wire mesh of the cage. The movements of the body were shaky and unsteady. Fits of convulsion, especially when the animals were irritated, soon followed. Feedings were poorly taken and emaciation became noticeable. After 2 or 3 days of excitement, weakness or paralysis of the hind legs usually could be noted. In some animals, however, paralysis was observed to start from the front limbs. The animals usually died in 2 to 5 days after showing the first symptoms of excitement. When the course is acute as in animals inoculated intracerebrally with high concentration (1:400) of the virus suspension, death may result in 2-3 days after development of excitement without showing weakness of limbs.The effectiveness of administration of the virus through different routes decreased in the following order: intracerebral, intramuscular, subcutaneous, and intraperitoneal. The first route was by far the most effective as fatal infection resulted with inoculation of virus suspension diluted as high as 1 to 1,000,000. The incubation time and day of death varied with two factors, namely the concentration of virus suspension and route of its introduction. When concentrated virus suspension was given, the incubation time and day of death tended to be shortened. They were also shortest when virus was introduced intracerebrally but were lengthened by 2 to 12 days when virus was introduced through other routes.

A simple method for direct and accurate enumeration of bacteriophage is still lacking. In many instances it is desirable to determine the bacteriophage unit directly. For this purpose 2 general methods are now in use, (1) the counting of plaques formed when bacteriophage and susceptible bacteria are spread on the surface of agar plates, and (2) the determination of the highest dilution in broth for a given bacteriophage to cause complete lysis of susceptible bacteria. The best agreement by the dilution method of titration has been calculated by Clark1to be 60%. The difficulty of spreading evenly on an agar surface and the adsorption of a variable amount of bacteriophage by the spreader are the disadvantages of the streak method. If bacteriophage and susceptible bacteria are mixed thoroughly in meat infusion agar and then poured into plates, we find that the technique is not only simplified but its accuracy is also increased. It seems worthwhile, therefore, to test the practicability of the pour plate method and the optimal conditions for the demonstration of bacteriophage plaques under various factors of growth.A dysentery Shiga bacteriophage isolated from a single plaque was used. Pour plates were made by mixing 1 cc. of diluted bacteriophage, 0.5 cc. of an 18-hour agar slant growth of susceptible bacteria in concentration of 1:50 in saline and 15 cc. of 2% meat infusion agar (pH 7.6). Upon incubation at 37°C. for 24 hours. 2 kinds of plaques appear: (a) surface plaque, which is large, clear, and extending through the depth of the medium, and, (b) deep plaque, which is small, less clearly outlined, and situated below the surface.In agreement with Bronfenbrenner and Korb2we found the size of the individual plaque to be bigger as the concentration of agar is decreased (Fig. 1).

We have shown1that exposure to supersonic waves brings about killing and dissolution of certain bacteria. The question as to whether these effects are due to the mechanical waves motions in the medium or cavitation of the dissolved gases remained unanswered. The observations of the present study on the effect of supersonic waves on B. dysenteriaeShiga and B. colisuspended in gas-free solutions and in solutions saturated with air or hydrogen seem to indicate that the killing and dissolution of the bacteria is due to the cavitation of the dissolved gases.The apparatus used for the generation of the supersonic waves at the rate of 1.5 × 106times per second was the same as described by Wu and Liu.2One cc. of the bacterial suspension to be exposed was placed in a pyrex tube (20 mm. in diameter) containing a glass cooling coil through which cold water circulated. The temperature of the bacterial suspension throughout the entire experiment was always below 20°C, thus eliminating the possibility of destruction of bacteria by heat. Twenty-four-hour cultures of B. dysenteriaeShiga and B. colion agar slant were washed and suspended in saline. To make the suspension gas-free, it was placed in the test tube and subjected to suction with a vacuum pump until the mercury manometer showed a constant minimum reading of 18 to 20 mm. The rubber tubing connecting between the test tube and pump was clamped and disconnected from the pump. The test tube containing the gas-free suspension under vacuum was then exposed to supersonic waves. To obtain hydrogen saturated suspension, hydrogen gas was allowed to pass through a sterile glass tubing with a cotton plug into the gas-free suspension under vacuum until one atmospheric pressure was reached.

Among the various media that have been advocated for rapid isolation of V. cholerae, the most widely used is the alkaline peptone enrichment medium which, however, is by no means perfect. During a cholera epidemic in Peiping in the summer of 1932, we felt that a more efficient medium was desirable. To meet this demand the following medium (phenolphthalein-starch solution) was devised, utilizing the unique property of rapid fermentation of starch by V. cholerae1in a highly alkaline solution in combination with an indicator as an index for its growth. As the cholera epidemic was over when the technique of preparation of this medium had been perfected, its efficiency was tested out on stools seeded with V. choleraeand gave satisfactory results.The medium is prepared by dissolving peptone (Witte) 2 gm., maltose 1 gm., potassium nitrate 0.5 gm., sodium carbonate (crystallized) 0.5 gm., sodium chloride 10 gm., and magnesium chloride (crystallized) 0.5 gm. in 900 cc. of distilled water. The solution is boiled for 3 minutes and filtered. 100 cc. of a 5% solution of soluble starch previously boiled for 2 minutes is added to 900 cc. of the above solution and mixed thoroughly. The mixture is filtered through cotton and then through asbestos filter, yielding a clear filtrate which is first measured and then sterilized by boiling for 3 minutes. (The solution cannot be autoclaved in the ordinary way as the starch is decomposed by prolonged heating). The sterilized filtrate is kept in ice chest. Just before use the reaction of the solution is adjusted to pH 9.0-9.2 in the following way: First 5 cc. of the indicator phenolphthalein (saturated solution in 50% alcohol) is added to each litre of the filtrate and the solution is carefully brought to decolorization point (pH 8.3) by addition of necessary amount of N/20 HCl or N/20 NaOH and finally to each litre of the decolorized solution is added exactly 1.5 cc. of N/I NaOH which brings the solution to pH 9.0-9.2 (pink colored).

Destruction of living organisms by supersonic waves has recently been observed.1The mechanism of the destruction is, however, unknown. The present communication extends the observation to a number of pathogenic and nonpathogenic bacteria and the results seem to indicate that the destruction is due to the dissolution of the bacterial cells.The oscillating circuit was similar to that described by Wu and Liu,2and the quartz was adjusted to vibrate at the rate of 1.5 × 106times per second. Bacterial suspensions to be exposed were placed in a thin test tube, 15 mm. in diameter. Inside the test tube was placed a glass cooling coil through which cold water circulated. The temperature of the bacterial suspension was never over 20° C. The possibility of destruction by heat was therefore eliminated.Saline suspensions of the following 10 strains of bacteria were used: Bacillus subtilis, Bacillus anthracis, Bacillus proteus X19, Bacillus coli communis, Bacillus typhosus, Bacillus dysenteriae Shiga, Staphylococcus aureus, Micrococcus catarrhalis, Bacillus influenzae, and Streptococcus hemolyticus. The number of surviving bacteria per cc. before and after exposure was determined by counting the colonies in poured plates. In the case of Bacillus influenzaestreak plating was used. Control experiments with bacterial suspension standing at room temperature without exposure showed no significant change in the number of surviving bacteria. Results are shown in Fig. 1.

For the cultivation of Leishmania donovania number of media generally containing blood have been advocated. In such media only flagellate forms are found. It is of interest to record the growth of Leishmania flagellates in media of various embryonic chick tissues which have not hitherto been used for the purpose.The chick embryos employed were fertilized hen's eggs incubated at 37°C. for a varying period of 4 to 20 days. The embryonic chick brain, heart, liver and intestines were removed separately and chipped into fine pieces with sterile scissors in different dishes. They were then suspended in sterile Tyrode's solution having a pH 8.0 in approximate concentration of 0.5 gm. of tissue to 10 cc. of fluid. In some experiments the whole chick embryo from 4 to 7 days old minced finely and suspended in Tyrode's solution was used. With a sterile capillary pipette one drop (about 0.15 cc.) of the embryonic tissue suspension was placed in the center of sterile cover-glass. To this was added a similar drop of Tyrode's solution containing Leishmania donovanifrom the spleen of an infected hamster. A sterile hollow glass slide measuring 7.5 cm. long, 2.5 cm. wide, and 0.7 cm. thick, with a central pit or well, 1.8 cm. in diameter and 0.4 cm. deep, was smeared with sterile vaseline around the mouth of its well. The hollow glass slide was then inverted over the cover-glass in such a way that the inoculated media fluid on the cover-glass faced the center of the well of the hollow glass. The whole slide together with the cover-glass was then turned over by quick motion so that the hanging drop did not spread to the periphery but remained in the center of the under-surface of the cover-glass. Pressure was gently applied to the latter to ensure airtight sealing of the hanging drop inside the hollow glass. Many such hanging drop preparations were made and incubated at 37°C. and at 20°C. in separate lots. The advantage of such hanging drop cultures is obvious. It permits direct microscopic examinatiion at frequent intervals without contamination.

From the observations of Tillett and Garner1and Madison,2the fibrinolysin from human strains of Streptococcus hemolyticusseems to act specifically on human plasma or fibrin-clots. Although Tillett and Garner have noted exceptional instances of slow dissolution of rabbit fibrin clots by culture of Streptococcus hemolyticus, the homologous rabbit plasma or fibrin clots are generally found to be resistant to the fibrinolysin while clots composed of human and rabbit heterologous fibrinogen-thrombin complexes are readily liquefied by it. The mechanism responsible for the resistance of the homologous rabbit fibrin-clots to action of the fibrinolysin is still unexplained. In an attempt to throw some light on this point, the present experiment was carried out with the use of concentrated streptococcus fibrinolysin.Six strains of Streptococcus hemolyticus, isolated from sore throat and scarlet fever cases, were used for production of fibrinolysin. Sixteen hours growth of the culture in meat-infusion broth (initial pH 7.6) containing 1% dextrose was passed through a Seitz filter. The filtrate was concentrated according to the alcohol precipitation technique of Garner and Tillett.3The precipitate after first alcohol precipitation was washed once with a fresh lot of cold 95% alcohol and recollected by centrifugation. The recollected precipitate was first dried by a vacuum suction pump and then redissolved in saline to a volume equal to 1/40-1/20 that of the original culture filtrate. The insoluble particles in the solution thus obtained were removed either by filtration through filter paper or by centrifugation. The clear filtrate or supernatant fluid was a highly concentrated fibrinolysin solution and was used for tests in the present experiment. Fibrinogen and thrombin from plasma of man, rabbit and guinea pigs were prepared according to the method used by Tillett and Garner.

Although the rôle of histamine in anaphylaxis is still disputed, the resemblance between symptoms in fatal anaphylaxis and histamine shock has been pointed out by Dale and Laidlaw1and histamine-like substance in anaphylaxis has been demonstrated in guinea pig by Bartosch2and in dog by Gebauer-Fuelnegg and Dragstedt.3In the present study an attempt has been made to compare the histamine destroying power (histaminase4) of whole blood of guinea pig, rabbit, dog and man, and to see if any correlation may be made between the humoral destruction of histamine of these species and their relative susceptibility to histamine.Freshly drawn blood samples were defibrinated by shaking with glass beads for 5 to 10 minutes. Varying amounts of blood were mixed with 1 cc. normal saline containing 1 mg. histamine acid phosphate (ergamine) and saline was added to make volume of the samples uniform in each experiment. After adding a few drops of toluene, the mixture was incubated at 37°C, for 24 hours. At the end of incubation the histamine content in the mixture was determined by Dale's blood pressure method (Burn5) in atropinized and doubly vagotomized cats under luminal anesthesia. Control blood samples (without addition of histamine solution), blood samples heated to 70°C. for 10 minutes before addition of histamine solution, and standard histamine solution (without addition of blood) were also incubated for 24 hours at 37°C. before the test.No control blood samples (without addition of histamine) showed any depressor effect on the cat, and no heated blood samples any histamine destruction activity. From the blood of 22 guinea pigs, 10 rabbits, 3 dogs, and 3 men, the following results were obtained. The rabbit blood showed maximum histamine destruction at 5 cc, dog at 10 cc. On the other hand, guinea pig blood showed no detectable destruction of histamine at 30 cc. Similarly, human blood showed no destruction of histamine up to 100 cc. Graph 1 gives the actual data.