HYPOPHYSIS AFTER CASTRATION 455 



which is very different from the more compact and uniform 

 structm-e of the normal. Measm-ements of the largest vacuoles 

 average 19 x 14.7 m, and these are in ring-shaped cells, measuring 

 23 X 18.8 fx, which is again distinctly larger than at five months 

 after operation. Of the other basophiles without vacuoles, 

 two varieties were seen, some coarsely granular, others finely 

 granular. The former measure 19.9 x 16 n, and the latter 

 measure 16.3 x 13.5 m- In the normal, also, at this age the baso- 

 philes were found to be of two varieties, some having finely 

 granular and others coarsely granular cytoplasm. Measure- 

 ment of these two varieties showed the finely granular here again 

 to be smaller than the coarsely granular (table 3). This sug- 

 gests that this differentiation of the basophiles may be here an 

 age phenomenon. 



In most regions the acidophiles seem distinctly fewer and it 

 appears that many of this type of cell have lost their characteris- 

 tic staining and now appear more or less like reserve cells. 



DISCUSSION OF OBSERVATIONS 



In the albino rat hypophysis, as we have seen, there are three 

 distinct types of cells, — (1) acidophiles, (2) basophiles, and 

 (3) the remaining cells tentatively classed together as reserve 

 cells (chief cells). These last during histogenesis and the early 

 growth of the organ are continually being differentiated into the 

 two functionating types. Small groups of these reserve cells 

 are still present during mature life, and lie dormant until stimu- 

 lated by the needs of the organism. The removal of the testes 

 we have found to increase the size of the basophiles, and 

 also the number of basophiles, and we believe these new baso- 

 philes to come from reserve cells. It is conceivable that, up 

 to a certain time in the life history of these reserve cells, they 

 are all similar and have an equal potentiality for becoming 

 either acidophiles or basophiles. It is possible that this capacity 

 persists after maturity is reached and throughout life, but it may 

 be that at maturity each has acquired a tendency to become 

 definitely of one or of the other type. In our observations, in 

 addition to some reserve cells becoming basophiles, it has ap- 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 28, NO. 2 



