29(5 CHARLES R. STOCKARD AND A. L. JOHNSON 



and hunting instincts of the bassethound are closely the same 

 as those of an ordinary hound. 



The English bulldog, with its various growth distortions, 

 forms an almost perfect contrast to the bassethound. The 

 extremities in the bulldog are stocky and straight, and the 

 long bones of the leg give no evidence of chondrodystrophy, 

 either from genetic or morphologic examinations. In this 

 dog, the head and the tail, the two opposite ends of the axial 

 skeleton, show distortions due to chondrodystrophy in the 

 basicranium of the skull and the epiphyseal cartilages in the 

 vertebrae of the tail. The intermediate parts of the axial 

 skeleton are usually perfectly normal, but in unusual cases 

 chondrodystrophy in the cervical and other regions of the 

 vertebral column has been found. To our knowledge, how- 

 ever, the long bones of the extremities in the bulldog are 

 never achondroplasic. The instincts and behavior of the bull- 

 dog are not entirely those of a normal dog; it has almost lost 

 the hunting instinct, and its breeding reactions are frequently 

 defective. 



The question arises whether these modifications in nervous 

 function are the results of the structural distortions and 

 abnormal endocrine conditions in the bulldog. We hope to 

 give at least a partial answer to this question in the pages 

 beyond. 



In view of these localized growth modifications in the 

 bodies of animals otherwise normal in gross structure, it 

 seemed theoretically possible that other and even more sharply 

 localized modifications and combinations might be obtained 

 by cross breeding such dogs with contrasted characters. For 

 example, in hybrids from such cross breedings, the head of 

 the bulldog might be associated with the short legs of the 

 bassethound; or the bulldog head might occur in an animal 

 with long, straight, normal tail; or, still more important, the 

 short, bent "screw-tail" might be produced as the only devia- 

 tion from normal. Is it possible for chondrodystrophic growth 

 to occur onlv at the head end or only at the tail end of the 



