GENETIC TYPE AND THE ENDOCRINES 467 



removal of its own pituitary would in no wise transform the 

 dachshund into a Boston terrier. Also justified is the further 

 inference that injections of identical pituitary hormones into 

 the Boston terrier will induce responses somewhat different 

 from those elicited in a dachshund, if it induced any at all. 

 Evidence in substantiation of these inferences has been given 

 in Section III where it was shown that in spite of the fact 

 that the same endocrinic milieu prevails throughout the body, 

 genetic constitution may determine distortions of growth in 

 localized body parts while normal form is attained in other 

 regions. The several structural disharmonies arising in hy- 

 brid combinations, as discussed in Section III, also add im- 

 portant evidence in support of the above statements, and still 

 more direct facts relative to the varying effects of the same 

 hormone on individuals of different types are already being- 

 accumulated in our experiments. 



If the Boston terrier and dachshund types show probable 

 correlation with certain histologic patterns of the pituitary, 

 does this also apply in connection with other endocrine glands? 

 Photomicrographs of sections of the thyroid glands from the 

 two opposite typed F 2 hybrids supplying the pituitaries just 

 discussed are shown in figures 3 and 4 of plate 89. Figure 3 

 is from 1523 $ , seen from life as the right animal in figure 9 

 of plate 30. This dog had a long muzzle, long straight tail 

 and short legs, and is a still better dachshund in type than 

 his brother, shown less reduced as figure 7 in plate 30. The 

 thyroid section shows the histologic pattern generally char- 

 acteristic of long muzzled breeds and especially of the dachs- 

 hund (see fig. 3, pi. 84 and fig. 1, pi. 85). 



Figure 4 of plate 89 illustrates a thyroid histology clearly 

 contrasted with figure 3 and is in every detail a striking 

 example of the Boston terrier gland pattern (fig. 2, pis. 82 

 and 85). The F 2 bitch which supplied the short and rounded 

 cystic pituitary and this thyroid with its small, irregular 

 and numerous tiny follicles and nests of parafollicular cells 

 lying among the follicles, also possessed, as we have said, 

 Boston terrier-like head and an undershot lower jaw. 



