genetic type and the endocrines 475 



Developmental Arrests and the Quality of Differentiation 

 in the Parathyroid Glands of Boston Terrier- 

 Dachshund Crosses 



Modifications in bodily size, types of growth and quality 

 of bone are known to result from thyroid deficiency through 

 the experimental studies of Dye and Maughan ('29) on dogs, 

 and of Todd, Wharton and Todd ('38) on sheep, as well as 

 through numerous other contributions to this problem. Dis- 

 eases of the pituitary gland have been known for many years 

 to cause similar modifications in both size and shape of the 

 skeletal framework of the body, and in many cases it is 

 difficult to determine which of the two glands — thyroid or 

 pituitary — is directly responsible for the growth modification. 

 However, the weight of evidence at present attributes this 

 influence largely to the pituitary gland, even in those cases 

 where the initial conditions are thyroid deficiency or com- 

 plete absence of thyroid, the result of which tends to reduce 

 and disbalance pituitary functions. Numerous studies on 

 rickets and the disturbances of calcium metabolism involved 

 in the distortion of bone composition have pointed to the 

 parathyroid glands as a serious factor for consideration in 

 some growth abnormalities. Reports on the pathology of 

 the parathyroid in cases of severe rickets, and the experimental 

 studies of Nonidez and Goodale ('27) on the effects of ricket- 

 inducing diets in birds have shown that the parathyroid 

 glands undergo a primary hypertrophy with true hyperplasia 

 followed by degeneration and complete obliteration of the 

 normal secretory epithelial cells, thus suggesting that these 

 glands must play an essential role in the growth and develop- 

 ment of normal bone and body types. 



In view of these facts, the modifications in size and pattern 

 of the axial skeleton of the Boston terrier, and the appendicu- 

 lar skeleton, particularly the long bones of the extremities, 

 in the dachshund forces us to investigate the quality of 

 parathyroid glands in these breeds witli the same interest 

 as we have the thyroid and the pituitary and their relation 



