444 



WILLIAM H. F. ADDISON 



expansion of this part of the hypophysis. Beginning cephalad 

 where the largest vessels are seen, these branch and break up into 

 a sinusoidal network, which extends throughout the substance 

 of the gland. 



The connective tissue framework is very slight, and there is 

 no definite division into groups of cell masses by connective tissue 

 septa, as is seen in man and many other species. 



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4 







Fig. 1 Median sagittal section of hypophysis of albino rat showing (/) 

 pars nervosa, or infundibular portion; {2) pars intermedia, or juxta-neural 

 portion; (3) pars anterior, or ventral glandular portion; (4) pars tuberalis; 

 (5) lumen of residual pouch of Rathke. X 40. 



The differentiation of the cell-types occurs in the first month of 

 post-natal life. At birth neaHy all cells are of similar appear- 

 ance, and still resemble the primitive fetal type. Here and 

 there, examples of two other cell-types may be seen developing 

 from the undifferentiated type. At the end of one month, 

 however, differentiation is well advanced, and the three types 

 are easily recognized. These three types are: (1) acidophiles, so 

 named from containing numerous small closely-packed granules, 

 which stain with acid dyes and especially well with acid fuchsin; 

 (2) basophiles, larger cells than the preceding with cytoplasm 

 moderately basophilic; and (3) unchanged descendants of the 

 primitive fetal type, which may be termed reserve cells. 



