VARIATIONS IN PROPORTIONAL SIZE AND MODIFICA- 

 TIONS IN HISTOLOGIC QUALITY OF ENDOCRINE 

 GLANDS IN RELATION TO BODY TYPES AS 

 FOUND AMONG THE DOG BREEDS 



For several years before beginning the experimental part 

 of this study, the endocrine glands from dogs of pronounced 

 types were collected at the New York city pound. Since the 

 exact ancestry and breed purity of such animals were un- 

 certain, only those specimens showing well pronounced physi- 

 cal characteristics of the various breeds were selected. From 

 a study of this material it became evident that the highly 

 modified and deformed breeds, such as the achondroplasic 

 bulldog types, showed marked abnormalities in the histologic 

 structure of the thyroid and other glands. This evidence 

 strengthened the initial idea that many dog breeds exhibit 

 physical characteristics closely resembling the growth distor- 

 tions found in human beings suffering from diseases of the 

 endocrine glands, and we felt that the important problem 

 was to ascertain whether modified endocrine glands might 

 be the cause of hereditary growth distortions in the several 

 dog breeds. Many secondary problems arising from this gen- 

 eral investigation have been presented in previous sections 

 of this paper. In this section the differences in gross pro- 

 portional sizes and in microscopic structure presented by 

 the endocrine glands of the various types of dogs will be 

 discussed. Evidence will then be given of the inheritance of 

 glandular size and quality as correlated with physical types 

 in the various breeds and their hybrids. 



Associated with the endocrinic modifications found in the 

 various pure breeds and their cross bred hybrids are many 

 very striking functional peculiarities. For example, certain 

 of the giant breeds, all of which have abnormalities of the 

 pituitary, show most irregular records for fecundity. Many 

 individuals in these breeds are poor producers, frequently 



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