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A group of Gaspé fishermen used to cold water immersion and control subjects from the same vicinity were studied to determine if the fishermen's hands were adapted to cold. With one hand immersed in cold water, the pressor response was greater in the control subjects; the fishermen maintained a higher finger temperature and complained less of pain; heat flow from the fishermen's hands was greater than in the control group; finger numbness as measured by a modification of Mackworth' V-test was variable and not significantly different in the two groups. Skin biopsies showed no difference in skin thickness or cell size but there was a significantly greater number of mast cells in the fishermen's skin. The differences between the fishermen and the control subjects may be related to repeated cold exposure. Submitted on June 7, 1960

To differentiate between the mechanisms which have been proposed to account for the hypotensive effect of pulmonary insufflation, cyclic volume changes of the right ventricle were qualitatively monitored by means of a variable resistance strain gauge sutured to the right ventricular wall. Artificially created decreases in venous return as well as cardiac tamponade of a degree sufficient to produce hypotension for brief periods were found to decrease the volume of the right ventricle. Increased right ventricular outflow resistance, however, produced a marked increase in right ventricular volume. With brief periods of hypotensive levels of pulmonary insufflation, right ventricular volume was found to increase in the animal with a wide-open chest; the volume decreased with the chest closed. It is concluded that in the open-chest condition the hypotensive mechanism of pulmonary insufflation is an increase in pulmonary vascular resistance, whereas in the closed-chest condition decreased venous return, cardiac tamponade, or both are predominantly responsible for the hypotension.

WHEN THYROXINE is injected into an animal and the bile assayed, definite amounts of iojiine may be detected, amounting in some experiments to an excretion within three hours after injection of as much as 47 per cent of the total quantity administered (Kendall 1919, Krayer 1928). Bioassay (by the method of axolotl metamorphosis) indicates that, while some of the iodine is present in an hormonally active form, there has been considerable destruction of the administered hormone (Krayer 1928). Chemical fractionation methods, on the other hand, indicate that as much as one-half to twothirds of the thyroxine may be excreted unchanged (Barnes 1933, Zawadowsky & Perelmutter 1927). It appears from these experiments that the liver is able either to excrete thyroxine in the bile, or to destroy the hormone and excrete the iodine in a physiologically inactive form.

Heart rates reported for Alligator mississippiensis at laboratory temperatures include those given by Blackford (1956) as 35 and 50 beats/minute; Obrist and Chow (1956) as 25-30 beats/minute; Wilber (1960) as 40 beats/minute; Andersen (1961) as 2441 beats/minute; Akers and Preiss (1963) as 18 beats/minute; Coulson and Hernandez (1964) as 26-43 beats/ minute, Campos (1964) as 22-30 beats/minute; and Boyer (1966) as 40 beats/minute. Rates from early unpublished data in this laboratory averaged about 31 beats/minute with a range of 20-48, but later in long-continued studies much lower rates were seen. Em

Five isolated canine heart-lung preparations were successfully ventilated with intermittent negative pressure in a specially constructed chamber. Improved cardiopulmonary dynamics resulted in increased survival time and improved performance of all preparations. Results obtained with these preparations exceed most of the others reported in the literature. Submitted on May 9, 1960

(1936). Galvani and the pre-Galvanian electrophysiologists. Annals of Science: Vol. 1, No. 2, pp. 157-172.

A NUMBER OF sulfonamides and thiourea derivatives produce a goitrous hyperplasia of the thyroid accompanied by a marked decrease in basal metabolism (Richter and Clisby, 1942; MacKenzie and MacKenzie, 1943; Astwood, 1943). These actions have been attributed to a suppression of the thyroid secretions by the drugs. If this is the case, effects of thyroidectomy, such as bradycardia and atrophy of the kidney and other organs, should also be obtained with these drugs. It was therefore decided to investigate the action of representative sulfonamide and thiourea derivatives on the heart and other organs, as compared to that of thyroidectomy. In a preliminary experiment, 30 rats weighing from 90 to 130 gm. were divided into 3 groups. One group received a 1 per cent solution of thiourea as drinking water; another group was thyroidectomized; the third group was used for control.

For the transmission of physiological data not requiring complete freedom for the subject, a direct wire system offers many practical advantages including low cost and high reliability. Such a system is particularly well adapted for bedside monitoring and for the usual studies in the clinical laboratory where the patient is required by his illness to be in a fixed position. For general purpose physiological telemetery, it is necessary to transmit a bandwidth extending to zero cycles per second. Experience has demonstrated that such transmission is possible over a direct wire circuit for a distance of at least half a mile. An over-all response time of 100 ?sec provides an adequate bandwidth for the most rapidly changing physiological events.

Transmembrane action potentials were recorded from embryonic rat hearts at ages between 10½ days of gestation and birth (21 to 22 days). The resting potential averaged 30 to 40 mv at 10½ days and increased to around 80 mv by birth. Two periods of rapid increase in resting potential were noted: 1) from 10½ to 13½ days and 2) from 19½ days of gestation to birth. The maximal upstroke velocity of the action potential increased as the resting potential increased. The duration of the ventricular and atrial action potentials was inversely related to heart rate, and their rate sensitivity decreased with age. The atrial action potential lost its rate sensitivity by 13½ days of gestation and the ventricular action potential lost its by birth. At 10½ days diastolic depolarization was found in the area of the ventricle proximate to the A-V junction, the left and right atria, and the sinus venosus. The velocity of the diastolic depolarization was greatestin the sinus venosus and least in the ventricle. The diastolic depolarization decreased with growth and was lost by 13½ days of gestation.

A miniature, transistorized radio-frequency-coupled cardiac pacemaker was developed to eliminate wires penetrating the skin when electrodes are placed on the heart to drive it. The design also eliminates the need for totally implanting a pacemaker with its batteries. The stimulating impulse is transmitted via amplitude modulation to a tuned circuit and detector assembly implanted below the skin. The output of the detector is connected to electrodes directly on the heart, making external control of the heart rate possible. In operation, the pacemaker transmitter is placed on the surface of the body above the receiver implant. The size of the unit is 4×13/4 ×13/2 inches. It weighs three ounces.

In experiments previously reported, it was found that application to the surface of the heart (cat, dog, rabbit) of squares of filter paper soaked in M/10 or M/5 KC1 solutions, produced changes in the electrocardiogram similar to those which follow various types of injury to the heart, except that the potassium effects quickly subsided following removal of the solution.1 Generally accepted views of the action of potassium ions in the heart and elsewhere suggest that the electrocardiographic changes produced by the application of potassium to the surface of the heart result from the reversible extinction of the action current at the point of application. Potassium chloride has in fact been employed to abolish electrical activity at selected regions in muscle and thus to permit recording of monophasic action currents.2We have performed a series of experiments to determine whether potassium has a similar effect when applied to the surface of the heart, and found that we could obtain monophasic action current...

A 19 year old female human subject with complete heart block was put at complete bed rest for 63 hours during which a Lead II EKG was monitored at half hour intervals. Atrial and ventricular rates demonstrated cyclic activity with peaks during the day and troughs during the night. A correlation coefficient of plus 0.85 and a slope of plus 1.0 from a linear regression between atrial and ventricular rates demonstrated a close parallel. Calculation of the crosscovariances confirmed the observed cyclic activity with a period of 24 hours and phase angle of zero degrees between the two chambers. The data may be explained by one or all of the following mechanisms: (1) both chambers are subject to the same internal milieu, (2) autonomic nervous system discharge and associated reflexes may integrate relative changes in rate, (3) direct mechanical or electrotonic forces may result in alteration of rates in direct proportion to the magnitude of the dominant chamber, (4) program which operates independent of external factors. The question remains for direct experimental data to demonstrate whether the observed phenomenon is an intrinsic biologic rhythm within the heart or in its control system.

Summary In complete A-V block a type of arrhythmia occurs in which atrial cycle length or instantaneous rate is a function of the presence and position of a ventricular QRS complex within that cycle. The immediately following atrial cycle without QRS is invariably longer than the preceding atrial cycle. The so-called PR interval has been plotted against two consecutive atrial cycles, the initial cycle which contains the PR and QRS, and the immediately following cycle without QRS. Both atrial cycles were then plotted against each other to demonstrate their relation. Linear regressions were performed and the correlation coefficients computed. The mechanism of the interaction of atria and ventricles in complete block has not been completely settled, but several proposals have been made among which the more promising include: a vagal reflex arising from baroreceptor stimulation, traction of one contracting chamber on the other, and electrotonic or “field effect” induction. The observed phenomenon has been studied statistically, several previously unreported observations have been made, and an attempt has been made to interpret the phenomenon in terms of the several proposed mechanisms.