The morning urinary surface tension was measured in four groups of 40 rats each: one group of 20 males, one of 20 females of the white Wistar strain, one group of 20 males and one of 20 females of a black "hooded" strain. From the data obtained on each group, the average value was calculated and its respective curve traced. The four curves were seen to be parallel, suggesting that the variations noted result from the intervention of a common external factor. We sought this factor in the changes occurring in the environment. For this reason, we compared the variations present in the surface tension curves with the meteorological data, furnished by the U. S. Weather Bureau, corresponding to the time of this experiment. Such a relationship was seen to only partially parallel the barometric changes, but appeared more closely related to the temperature changes. The observed relationship however, is inverse, that is, for higher environmental temperatures the surface tension values are low whereas for lower environmental temperatures, the surface tension values are high, as seen in Fig. 223. (Page 586)

This correlation appears still more interesting when it is compared to that induced by keeping animals at a constant temperature, as in an incubator or in a refrigerator. The effect of such an induced temperature is opposite to that caused by the environment. The high temperature of the incubator induces progressively higher surface tension values while the low temperature of the refrigerator lowers the surface tension, at least at first. Fig. 224 shows the average value of the urinary surface tension in controlled animals, while Fig. 225 that of the animals kept in an incubator at a temperature of 37°C and in a refrigerator at 8°C. (Page 588)

We tried to explain this discordant influence between the induced and natural temperatures, through the fundamental characters of these two factors. In the influence exerted by the environment, temperature with its variations, represents a factor which has acted upon organisms with the same rhythmic characters for many millions of years, while in the experiments, the constancy of the temperature represents its main character.

The influence exerted by the rhythmic environmental changes in air temperature is reflected in the parallel body temperature. The organism still tries to control this influence as exerted upon the lower levels. This is seen in rats in the opposite rhythmic changes of the urinary surface tension values. The organisms appear sufficiently sensitive to changes in temperature occurring in the environment. The body responses oppose these changes as shown in the variations in urinary surface tension. This rhythmic response, as well as that opposing the variations in the environmental temperature, are broken when a continuously unchanged high or low temperature is applied. With the reactional response exhausted after a certain time, the influence exerted appears a direct one, the high temperature inducing a high urinary surface tension and the low temperature a low one.

Relationship between the curves of serum and total blood potassium of a group of 20 subjects

Fig. 263. Relationship between the curves of serum and total blood potassium of a group of 20 subjects and the atmospheric temperature, humidity and barometric pressure. Parallel variations are seen between the curves of total blood potassium and of barometric pressure. An inverse relationship is seen with the curve of humidity, and only partial relationship to the temperature.

However, a difference is seen between the influence exerted by the high and low temperature. After some time, the animals kept in a refrigerator usually recover the capacity to fight the persistently low temperature, and the surface tension returns to normal values. This does not occur for the persistingly high temperature. The animals die with a progressively high surface tension as if the defensive response seen for low temperatures would not intervene for high temperatures.

This difference in the response of an animal toward a persistently high or low temperature can be explained by the fundamental difference which exists between these two factors from the point of view of homo- or hetero tropy. While the low temperature has a homotropic character, the high temperature has a heterotropic one. The bodies are basically more prepared to react successfully toward homotropic influences as they have done it for millions of years in the past, than to an entirely unusual heterotropic influence.

Chapter 6, Note 28. Barometric Influence

For several years, we studied the potassium content of blood red cells in subjects with various abnormal conditions, usually following it daily for the same patient for weeks or months. Besides other informations which this study furnished and which are discussed above, we want to emphasize now the relationship with barometric pressure which we were able to establish during repeated analyses on the same group of subjects. We were impressed by the parallel variations seen in the amount of potassium in the total blood of different patients on different days regardless of medication. The variations could be correlated with changes in the barometric pressures. With lower pressures, a decrease in the amount of potassium in total blood (Fig. 263) was noted. Less manifest changes were seen with the opposite variations in atmospheric humidity.