THE PARS BUCCALIS OF THE HYPOPHYSIS 15 



ent appearance from that furnished by the course black processes 

 of the normal melanophore. 10 



Not only do these superficial melanin-bearing cells exhibit 

 differences of a quantitative nature in these two types of ani- 

 mals, but constant physiological dissimilarity is also encountered. 

 It may be urged that the functional states of these cells in the 

 normal usually exhibit such wide variation not only between 

 two or more individuals, but also in the cells of a single indi- 

 vidual, that the determination of a normal physiological con- 

 dition is precluded. Certain it is that not only do we find 

 differences between the condition of the individual cells of a 

 specimen, but under identical environmental conditions these 

 cells in one animal may be expanded while those of its mates 

 are partly contracted. 11 Yet this variability is not so great as 

 to preclude our defining the condition of these cells in a normal 

 animal in an 'indifferent' environment as one of complete or 

 nearly complete expansion (fig. 13). 



With the albino, as with the normal, but to a lesser extent, 

 the same variability in the superficial melanophores of various 

 individuals is exhibited. The individual cells of any one speci- 

 men, however, usually exhibit a greater dissimilarity than in 

 the normal animal. A very few of these cells are almost in- 

 variably broadly expanded, a few are half expanded, while the 

 majority are completely contracted or but slightly expanded 

 (fig. 14). It is apparent, then, that the usual physiological 



10 The evidence on this point is quite clear; corroborative evidence has also re- 

 cently been furnished by Atwell, although Allen is apparently not in agreement 

 with these findings, for he says: "These observations and a careful study of the 

 pigment cells convince me that there is no disappearance and bleaching of the pig- 

 ment cells as asserted by Smith." It is worthy of mention here that the author has 

 never mentioned a "disappearance and bleaching of the pigment cells," stating, 

 "Counts of the epidermal melanophores — in the albinos and checks show that the 

 number of these cells in the epidermis is reduced in the former" and — "the melano- 

 phores of the albino specimens contain fewer pigment granules than do those of 

 the checks and thus have a distinctly lighter appearance." The process leading 

 to this condition was not then discussed by the author. 



11 This variability has led certain investigators to confine their observations in 

 various physiological experiments to the more uniformly reacting deep melano- 

 phores — for example, Laurens. 



