GENETIC TYPE AND THE ENDOCRINES 461 



indicate the dominance of the Boston terrier pituitary pattern 

 over the more normal dachshund type. To test the validity 

 of this indication, we studied pituitaries from thirty-three 

 second generation hybrids, at the same time attempting to 

 answer a question of even greater importance, that is, whether 

 specific differences in physical characters among the indi- 

 viduals are closely linked and associated with definite devia- 

 tions in the histopathology of the pitnitaries. 



The possible relation of differences in pituitary structure 

 to differences in physical type among the F> hybrids of the 

 Boston terrier-dachshund cross. The gross relative sizes of 

 the pitnitaries from thirty-three F 2 Boston terrier-dachshund 

 hybrids range from a low of 8 milligrams per kilogram of 

 body weight to a high of 26, the latter being more than three 

 times that of the former. These pituitary proportions are 

 shown in text-fignre 82 (p. 415), which has been previously 

 examined. The relative proportions for pituitary size shown 

 in this chart are independent of possible sex influence, as 

 is indicated by the fact that four of the five lowest as well 

 as four of the five highest represent male pituitaries, and 

 males and females are distributed irregularly throughout the 

 scries. Nor do cystic conditions seriously affect these relative 

 sizes; when the cysts are large the amount of anterior pi- 

 tuitary tissue is diminished. Differences in relative amounts 

 of total pituitary tissue are real, and on examining the F 2 

 series in the chart one might be led to admit the possibility 

 of an irregular tendency for the long muzzled dachshund 

 type to predominate at the high end of the series. But this 

 type also occurs in almost the lowest recorded relative pitui- 

 tary weight. As has already been concluded on the basis of 

 other evidence, it is highly improbable that the relative 

 amounts of total pituitary substance are of serious conse- 

 quence in the determination of growth and structural char- 

 acteristics in the mammalian body. This conclusion is entirely 

 aside from the question of the important effects that may 

 result from variations in the relative amounts of the several 

 hormones emanating from the pituitary gland, and we should 



