Temperature Regulation in Albino Rats Correlated with Determinations of Myelin Density in the Hypothalamus. ∗

Abstract

Conclusions

The optical densities of sections of the hypothalamus stained by modifications of the Weigert method have been measured in rats varying in age from 6 to 70 days by means of monochromatic light and an electronic photometer. These measurements have been correlated with the abilities of the animals to regulate their internal temperatures when exposed to a cold environment. We believe that our method has recorded densities which are dependent mainly upon the amount and/or character of the myelin in the hypothalamus at the respective ages studied, and that the increase in myelin from birth to 20 days of age may contribute to the acquisition of the capacity for temperature regulation. We do not believe that myelination in the hypothalamus is the only factor concerned in the acquisition of this function. Many other factors are no doubt operative and many of these are currently being investigated.