GENETIC TYPE AND THE ENDOCRINES / 



fications in the higher animals. The understanding of such 

 processes in grossly modified types can undoubtedly aid our 

 understanding of the slight expression of these tendencies 

 which exists in almost all so-called normal or ordinary in- 

 dividuals. 



Modern dog breeds have been developed entirely by sports- 

 men and "fanciers" who have carefully selected and bred 

 the various strange mutations spontaneously occurring in 

 the stocks. Many of the stocks were probably of hybrid 

 origin. After the breeds have once been established, they 

 are perpetuated and perfected by careful selection. Many 

 breeds are now old and highly homogeneous in genetic quality, 

 as our experiments will show. Fortunately for the experi- 

 menter, in many cases the dog breeds have been established 

 and handed over to us with more than a century's start toward 

 the analysis of our present problem. The lifetime of an 

 investigator would scarcely be long enough for the prepara- 

 tion of the breed stocks, even had the mutations from which 

 they arose appeared before his eyes. 



Only a few scientific studies on the genetics of the dog- 

 breeds have been made, and of these few none has had as 

 its aim the problems now under consideration. There have 

 been several studies of color inheritance in dogs, among 

 which are those by Warren ('27) on the greyhounds, Little 

 and Jones ('19) on the great Danes, Darling ('32) on bull 

 terriers, Darling and Gardner ('33) on Irish wolfhounds, and 

 Dahl and Quelprud ('37) on the German boxer. Plate ('30) 

 studied the inheritance of hairlessness, hair color and erect 

 ears in crosses between the hairless Ceylon dog and the 

 dachshund, but gave no consideration to the possible endocrine 

 implications. A short report was published in 1910 by Lang 

 on a cross between a St. Bernard dog and a dachshund. This 

 single hybrid litter exhibited points which might have been 

 of interest to our present problem, but the breeding was not 

 continued and the condition of the internal secretions received 

 no consideration at all, nor could it have been appreciated 

 from our present standpoints at that time. The study by 



