124 ANATOMY 



As the data show, the number of corpuscles increases from 

 birth up to somewhere between three and seven weeks of age, 

 after which it remains fixed though the kidney may increase 

 greatly in weight after this period. 



The volume of the cortex is from 1.5 to 3.0 times that of the 

 medulla, but the combined volume of these two portions rep- 

 resents on the average only about 50 per cent of the volume of 

 the fresh kidney. This indicates that fixation (Zenker's fluid) , 

 with subsequent treatment, and exclusion of the capsule and 

 pelvis have greatly reduced the measured volume. The deter- 

 minations therefore represent relative rather than absolute values. 



Sex organs, (a) Male. See tables 146, 147, and 149. 



(b) Female. See tables 146 and 150. 



11. Exocrine glands. Myers, 1916-1921, has recorded a num- 

 ber of observations on the structure and arrangement of the 

 mammary glands. There are usually twelve mammary glands, 

 six pairs, designated from the head caudad, as the 1st, 2nd and 3rd 

 thoracic pairs, the abdominal pair and the 1st and 2nd inguinal 

 pairs. Variations in the number of glands occur. There may be 

 only ten or as many as fourteen. After birth there are no external 

 indications in the male of the mammary gland areas. At birth 

 an inguinal and a thoracic fat pad or girdle are clearly marked. 

 These pads are similar in both sexes and are related to the loci 

 of the mammary glands in the female (Myers and Myers, '21). 

 The glands enlarge during the nursing period but shrink after 

 the young are weaned. Immediately after removal of the 

 young the glands enlarge and remain so for forty-eight hours 

 and then return to the virgin size in from two to three weeks 

 (Myers and Myers, '21). 



12. Endocrine system. Percentage of water. In the normal 

 hypophysis, thyroid and suprarenals Uno ('22) determined the 

 percentages of water, table 86. 



Hypophysis. Using for fixation the neutral formol Zenker 

 mixture of Bensley ('11) followed by paraffin imbedding, 

 Addison ('17) has measured the diameters of the several classes 

 of cells in the ventral glandular portion of the hypophysis 

 of normal male albinos at various ages. The results appear 

 in table 87. 



