ENDOCRINE SYSTEM 



159 



From this study the author concludes as follows : 



1. No increase in weight of the adrenal glands during preg- 

 nancy and lactation occurs in normal albino rats free from visible 

 signs of disease. 



2. An increase in weight of the adrenal glands occurs in un- 

 mated rats suffering from gross pathological lesions represented 

 by lung infections and infections of the middle ear. 



3. A further increase in weight of the adrenals occurs during 

 pregnancy in rats suffering from pathological conditions. 



The adrenals increase in weight several fold in animals starved 

 from 10-12 days, Vincent and Hollenberg, '20. 



TABLE 115 



Percentage deviations in the weight of the adrenals of pregnant and lactating albino 



rats. Based on body weight. Values in table 148 used as a standard 



(e) Thyroid and parathyroids. The amount of intestine con- 

 tracting substances in the thyroid of the rat according to age has 

 been studied by Hammett and Tokuda ('21). The duodenal 

 segments, prepared with precautions determined by Hatai and 

 Hammett ('20), were standardized in a solution containing 0.25 

 cc. of M/10 Nao C03 and the shortening induced by a like con- 

 centration of thyroid extract was expressed as a percentage of 

 the standard value. The results are presented in table 116 and 

 chart 19. 



In general the extract produces an increasing amount of con- 

 traction up to about 150 days of age — after which the effect 

 diminishes rapidly. The response is more marked for the male 

 than for the female. There are however significant high values 

 at birth, weaning, puberty and during rapid growth — the female 

 leading. It is concluded that these changes in the thyroid ex- 



