GENETIC TYPE AND THE ENDOCRINES 501 



We have seen, in the Boston terrier and some of the Boston 

 terrier-dachshund hybrids, all animals of dwarf size, that the 

 pituitaries show symptoms of developmental arrests, with 

 cystic formations surrounded by undifferentiated hypophyseal 

 epithelium. In many such animals the normal canine type 

 is altered, and bizarre modifications with a general tendency 

 toward bulldog-like characters result. The features of the 

 normal sized English bulldog are distorted far beyond the 

 similar characteristics in the Boston terrier, and the thyroid 

 glands in both these breeds deviate from the normal his- 

 tologic pattern in characteristically different manners. At 

 present we are to examine the nature of the pituitary in 

 the bulldog and to determine its behavior in the bassethound- 

 bulldog hybrids as compared with that of the thyroid, as 

 well as to make general comparisons with what has been 

 learned of the pituitary in the Boston terrier-dachshund 

 crosses. 



Photomicrographs of longitudinal sections of the pituitaries 

 from the bulldog and the bassethound and their hybrid prog- 

 eny are shown in plate 95. The general morphology of the 

 pituitary of the bulldog differs somewhat from that of the 

 long muzzled breeds. Figure 2 shows it to be short antero- 

 posteriorly and thick dorsoventrally, being almost spherical 

 in shape rather than oblong and flattened as in other breeds. 

 The pars nervosa is particularly thick, and its dorsal surface 

 is covered only by the thin roof of the hypophyseal sac which 

 forms a double layer of pars intermedia and encloses a cleft 

 of the residual lumen. The general interpretation of the 

 development of such a condition in the adult might be as 

 follows : the formation and upward growth of the hypophyseal 

 sac from the stomodeal epithelium was snch as to produce 

 an unusually small area of the heavily thickened epithelium 

 which gives rise to the future pars distalis and pars tuberalis ; 

 meanwhile, as the wall of the over-dilated hypophyseal lumen 

 distended, the thin dorsal portion which forms the future 

 pars intermedia was much increased in area. The contact 

 with the infundibular process caused an over folding of this 



