466 CHARLES R. STOCKARD AND E. M. VICARI 



obviously far below that contained in the F 2 gland at the 

 left. It is difficult, in fact, to realize that this cystic pituitary 

 can possess enough normally functioning tissue to supply the 

 basic needs of the mammalian body. Yet one can scarcely 

 doubt that it did, since this bitch lived a healthy kennel 

 existence for 3 years, and although never used for breeding, 

 expressed typical reactions of oestrus. Other individuals with 

 apparently equally bad pituitaries have served as sires and 

 dams in our experiments (see again photomicrographs of 

 pituitaries from such animals, plate 88 (figs. 1 and 5)). 



After an examination of these pituitaries from F 2 hybrids 

 1523 $ and 355 9 , it is quite evident that the gland from the 

 former closely resembles the dachshund histologic pattern, 

 while the distorted structures of the second pituitary tend 

 to be of the type commonly shown by the Boston terrier 

 gland. Further, these glands in the F 2 hybrids differ as 

 widely from one another as the glands of the dachshund differ 

 from the Boston terrier. As intimated above, the F 2 Boston 

 terrier-dachshund hybrids possessing these two quite dissimi- 

 lar pituitaries also differed in bodily appearance and in gen- 

 eral instinctive behavior in almost the same way as the 

 dachshund and the Boston terrier. The general appearance 

 of these two hybrid dogs and the histology of their pituitaries 

 would make it seem that the dachshund body type and pituitary 

 pattern are closely bound together; this likewise seems true 

 for the Boston terrier typed body form and pituitary pattern. 

 In line with this association of a given body type and a 

 definite pattern of pituitary histology, a study of a consider- 

 able number of F 2 animals showing various mixtures and 

 intergrades of the two types tends in large part to confirm 

 the above probability, and one is led to suppose that the form 

 of the head and body of the Boston terrier, as well as of 

 the dachshund, may be impossible of attainment except in 

 the presence of the given histopathology of the pituitary 

 gland. These relations lead back to fundamental differences 

 in genetic background, all of which indicate that a Boston 

 terrier pituitary transplanted into a dachshund following the 



