GENETIC TYPE AXD THE ENDOCRINES 481 



quality of osseous structures. We may now examine the 

 histologic nature of the parathyroid glands from the Boston 

 terrier-dachshund crosses. 



The photomicrograph of a section through one of the para- 

 thyroid bodies from a 6 year old dachshund bitch, 255 9 , is 

 shown in plate 91 (fig. 1) together with a similar section from 

 a 3 year old Boston terrier bitch 536 9 (fig. 2) for comparison. 

 Both sections appear fairly normal. The epithelial cells are 

 compactly arranged with clearly expressed patterns of 

 straight and curved cord-like bands. Connective tissue is 

 sparse and the vascular network is typical. Almost all the 

 epithelial cells are of the principal cell type characteristic 

 of the parathyroid, but at the mid-peripheral border in the 

 dachshund section there is an accumulation of bluish granular 

 cells seen as an irregular darker mass. This is not a constant 

 characteristic in the dachshund, and there is no difference 

 between the microscopic pictures of these two sections to 

 which any significance can be attached. In this respect the 

 parathyroid sections from the two breeds arc out of accord 

 with the histologic pictures of both the thyroid and pituitary 

 glands, which differed quite definitely. However, a longer 

 study of these glands might yield some differences in type, 

 and other parathyroid sections showing arrests and histologic 

 defects could no doubt be found in both these breeds. 



Figure 3 illustrates the parathyroid from a Boston terrier- 

 dachshund Fi hybrid. This gland has a considerably stronger 

 stroma of more abundant connective tissue than either section 

 from the parent breeds. The pattern of epithelial arrange- 

 ment is quite normal, and similar to that of the parent stocks, 

 although the photomicrograph is from a section nearer the 

 hilum and the larger vessels somewhat modify the picture. 

 A number of parathyroids from F x hybrids have been studied, 

 and all are fairly similar to figure 3. The differences between 

 the glands from two individuals are little if at all greater 

 than might occur among the separate parathyroid bodies 

 from the same individual. We have not yet been able to 

 consistently study all the parathyroid bodies from each in- 



