520 CHARLES R. STOCKARD AND E. M. VICARI 



adult animal from which this gland was taken is largely 

 hound typed although it possessed the screw-tail of the bull- 

 dog, as seen in plates 19 and 20 (pp. 97 and 99). A para- 

 thyroid section from a litter brother, 916 $ , is illustrated in 

 figure 2. Here again circles and whorls of the principal 

 cells are unusually marked, and irregular masses of bluish 

 cells are indicated by the dark spots near the periphery. 

 The cellular and vascular appearances in these two para- 

 thyroid sections are almost identical in detail, and yet the 

 F 2 hybrid brother and sister from which they came were 

 widely different in physical type. The brother, 916 $ , was 

 strongly bulldog in type with a heavy head and body and 

 stocky, wide spread legs; this animal is shown from life in 

 plate 19, and its skeleton in plate 20. The tall, hound-like, 

 graceful body of the sister, 918 2 , is widely contrasted with 

 the bulldog-like brother. Certainly these particular differ- 

 ences in physical types have no perceptible indication in the 

 closely identical histologic patterns presented by the para- 

 thyroid glands. 



Figure 3 in plate 98 illustrates the probable embryonic 

 nature of a large irregularly outlined cyst of branchial epithe- 

 lium. A distinct connective tissue coat surrounds the epithelial 

 wall, and the long more-or-less straight double row cords of 

 principal cells definitely radiate from the wall of the cyst 

 as if they were formed by columns of growth away from 

 the branchial epithelial base. As the periphery is approached, 

 toward the left part of the section, the cords are separated 

 by sinusoidal dilations of the capillaries. Darkly stained 

 bluish cells are shown in irregular groups in the vicinity of 

 the sinusoids. This parathyroid gland was obtained from 

 Fo bassethound-bulldog hybrid 902 9 when a mature adult 

 of I-T years. The bitch had short bassethound legs and a 

 slightly bulldog-like head with undershot lower jaw. There 



PLATE 98 



EXPLANATION OF FIGURES 



Bassethouncl-English bulldog cross. Further details of parathyroid histological 

 pattern in second generation hybrids. 



1 918$. 2 916 c?. 3 902$. 



