GENETIC TYPE AND THE ENDOCRINES 517 



birth the eight puppies increase at a rate of about one pound 

 per day for almost 6 weeks, being nourished solely by the 

 mother's milk. Translating this into terms of the production 

 within 9 months of a 7 pound baby by a woman of 120 pounds, 

 the performance of the bitch becomes astounding; on this 

 production basis the baby would weigh about 80 pounds at 

 birth. Undoubtedly the calcium metabolism of the pregnant 

 and lactating bitch is very highly taxed. 



The parathyroid of a bulldog is illustrated in figure 2 of 

 plate 97. This section is from a 4 year old bitch, 152 $ . The 

 cytoplasm of the principal cells in this gland is vacuolar in 

 appearance and so swollen that the cells are very large, and 

 double rows of nuclei distinguishing the cord-like arrange- 

 ments lie far apart. Marked differences in the size of the 

 principal cells among the parathyroid glands may be the 

 simple result of different states of functional activity at 

 the time of fixation, and in this bulldog parathyroid the cell 

 enlargement may be due either to high content of the secretory 

 product or to a vacuolar degeneration. In the case of a 

 Boston terrier-dachshund hybrid parathyroid previously dis- 

 cussed (tig. 5, pi. 91), the cytoplasmic content has been almost 

 exhausted, and the principal cells are of minute size as com- 

 pared with those in this bulldog section. Localized regions 

 of such cells with diminished cytoplasm are seen in many 

 parathyroids and may simply be those places from which 

 the secretion had recently been discharged. There is, how- 

 ever, the strong probability that certain breeds do possess 

 sluggish inactive parathyroids whose cells may be distended 

 by accumulated secretory products; other types may be 

 hyperactive with the cells discharging their secretion as 

 promptly as it is formed. The thyroid gland furnishes a 

 definite analogy in support of the latter interpretation, and 

 the above parathyroid differences may be typical rather than 

 due to periodic functional changes. 



A large branching sinusoidal cavity is seen near the surface 

 of the bulldog gland (fig. 2, pi. 97). This is filled with plasma 

 and blood corpuscles. Numerous capillaries lying between 



