The rôle of the nervous system in the regulation against cold. 1

One of us has shown that a dog placed in an ice-water bath up to the neck exhibits as one of the reactions to cold a concentration of the blood, losing approximately 10 per cent. of its blood fluid. Such extreme temperatures, however, even well-nourished dogs are unable to resist, the rectal temperature falling rapidly.

Investigating further the mechanism of regulation against cold we attempted to find first a bath temperature which, while not sufficiently cold to lower the body temperature, would arouse distinctly the regulation against cooling. Secondly, on dogs deprived of their nervous regulatory mechanism by section of the cord between the sixth and seventh cervical segment, it was attempted to determine whether the failure to resist the temperature of baths not too cold to be normally withstood is associated with inability to concentrate the blood.

It has been found that normal dogs will exhibit a fairly efficient regulation against cooling in a bath the temperature of which is maintained for a half hour or more at 20° C. In two such dogs there were net gains in body temperature as a result of exposure to the bath (respectively 0.1° C. and 0.4° C. in forty minutes). In a third animal the temperature fell 1.5° C. during the first twenty minutes but in the following thirty-five minutes showed a gain of 0.8° C., thus showing that the regulation against cooling was established after a delay.

In these three normal experiments the increases in blood solids were I, 2.1 and 1.8 per cent. respectively. The following table illustrates these points. In all of the experiments here reported the room was kept at a standard temperature of 22° C.

With the above should be contrasted the effects of similar baths upon three dogs with transection of the cervical cord, as shown in Table 11.