HYPOPHYSEAL MORPHOLOGY 



171 



granules are quite distinct from the secre- 

 tory granules. 



At one time the basophilia of basophil 

 granules was ascribed to ribonucleic acid. 

 It is now clear both from electron micros- 

 copy and from specific staining responses 

 that cells of the basophil class generally 

 contain less cytoplasmic ribonucleic acid 

 tlian do acidophil cells and that ribonucleic 

 acid is not a constituent of basophil gran- 

 ules. 



The cytoplasmic basophilia demonstrated 

 by the red staining by pyronin in the py- 

 ronin-methyl-green stain shows an entirely 

 different distribution from the basophilia 

 revealed by neutral toluidine blue or by 

 the Gram stain and it appears probable that 

 this pyronin-staining is specific for cyto- 

 jilasmic ribonucleic acid. Pyronin basophilia 

 is observed in all classes of cells of the an- 

 terior lobe and is increased in conditions 

 where rapid secretion rather than storage 

 is thought to be taking place. It is notably 

 increased in the large degranulated cells 

 observed in the hypophysis of pregnant ani- 

 mals and in animals treated by estrogen 

 (Herlant, 1943). 



Treatment for a short time with a ribo- 

 nuclease preparation will remove the py- 

 ronin basophilia without removing the 

 Gram-positive reaction or the violet meta- 

 chromasia with toluidine blue in the baso- 

 phil granules (Foster and Wilson, 1951; 

 Pearse, 1952). Prolonged exposure to bile 

 salts (Foster and Wilson, 1951) or ribo- 

 nuclease preparations (Pearse, 1952) will 

 remove the basophilia of the basophil gran- 

 ules, as well as the cytoplasmic basophilia. 

 This does not indicate that the basophilia 

 of the basophil granules is due to ribonu- 

 cleic acid. Pearse (1952) has demonstrated 

 the absence of ribonucleic acid in specific 

 basophil granules by means of the coupled 

 tetrazonium reaction. Acetylation for 8 

 hours blocks the reaction in the basophil 

 granules but does not block the reaction of 

 nucleolic and cytoplasm. 



VI. Cell Classes and Cell Types 



A. CLASSIFICATION 



Present knowledge has diminished some- 

 what the number of distinct adenohypo- 

 physeal hormones, and it seems possible 



that no more than six may have to be ac- 

 commodated in the pars anterior. These 

 are somatotrophin or the growth hormone, 

 prolactin or the lactogenic hormone, cortico- 

 trophin, thyrotrophin, FSH, and LH. It 

 seems probable from recent developments 

 that six cell types may be present in the 

 pars anterior. It is, therefore, profitable 

 to discuss pituitary cytology and its relation 

 to pituitary function on the assumption that 

 each hormone may be the single product of 

 a specific cell type. This may, or may not, 

 be true; a system of classification must not 

 be too rigid. 



The differentiation of the cells of the 

 anterior pituitary into acidophils, basophils, 

 and chromophobes must be regarded as a 

 differentiation of an unknown number of 

 specific cell types into three classes. 



The cells are classified by, and take their 

 names from, the staining reactions of their 

 specific granules. Even the smallest detect- 

 able amount of granulation serves for this 

 purpose, provided there is no confusion with 

 mitochondria or cytoplasmic basophilia. 



It may be noted here that it is usual to 

 say that cells are stained by a reagent when 

 they contain a large number of uniformly 

 distributed stained granules. This usage is 

 dangerous unless the convention is adopted 

 and rigidly adhered to that all staining re- 

 actions of cells, unless explicitly stated to be 

 otherwise, refer to the staining of specific 

 granulation. It is particularly important 

 when recording the absence of staining to 

 note and state if there are granules that are 

 unstained by the reagent. An absence of 

 staining when there is an absence of gran- 

 ules is not at all of the same significance. 

 The failure to differentiate between the 

 staining of granules and the staining of 

 other cytoplasmic components is a common 

 error. 



Cell types of the acidophil class contain 

 specific granules which have similar prop- 

 erties and, therefore, react alike to the 

 cruder staining methods. In the same way 

 the specific granulation of the cell types of 

 the basophil class have certain properties in 

 common which are to be ascribed to a simi- 

 larity in the chemical nature of the secre- 

 tions which enable them to be recognized as 

 a distinctive class. Chromophobic cells 

 whicli lack specific granulations of cither 



