484 CHAELES R. STOCKARD AND E. M. VICARI 



the origin and differentiation of the hypophysis from the 

 stomodeal epithelium are not uncommon. 



The parathyroid body and cyst just described were taken 

 from F 2 781 $ , shown from life as figure 7 in plate 39 (p. 236). 

 The other members of her litter are shown in plate 30 (figs. 

 1-5) (p. 129). The cranium and upper head of 781 $ is Boston 

 terrier-like in type, and is associated with a weak and atypical 

 muzzle. The life history of this animal was normal. The 

 small parathyroid body shows the general cord-like arrange- 

 ment of the principal cells, and at the periphery near the 

 cyst there are irregular groups of bluish staining cells, darker 

 in the photograph. These basophilic cells do not enter into 

 the cord-like arrangement. 



Figures 5 and 6 in plate 91 are parathyroid sections from 

 F 2 litter sisters, 354 $ and 355 $ , which are not illustrated 

 from life although an extremely defective litter sister, 353 $ , 

 is shown in plate 39 (fig. 3). Figure 5, from 354$ which was 

 killed at 3 years of age, is extremely different in histologic 

 appearance from the five other glands illustrated in plate 91, 

 The tubules or cords formed by double rows of epithelial 

 cells are strongly emphasized and facilitate a clearer under- 

 standing of the cord-like arrangements in the more normal 

 parathyroids. All parathyroid cords are formed by two 

 parallel rows of epithelial cells having their lateral surfaces 

 in contact with the walls of sinusoidal blood capillaries. In 

 this section the vascular walls are thickened, and an excessive 

 amount of connective tissue has infiltrated the parathyroid, 

 producing a trabecular-like pattern. The epithelial cells of 

 the cords are smaller and more tightly packed than in the 

 other glands. These conditions do not result from either 

 postmortem changes or fixation shrinkage, since the animal 

 was autopsied immediately after death and the gland was 

 fixed at the same time and in the same manner as the para- 

 thyroid from the sister, 355$ (fig. 6). The trabecular-like 

 arrangement may possibly indicate an exhaustion of para- 

 thyroid secretion, since the amount of cytoplasm is extremely 

 reduced. Localized areas showing this condition are fre- 



