488 CHARLES R. STOCKARD AXD E. M. VICARI 



essentially due to the fact that only one side of the epithelial 

 cell is in contact with a capillary; the other side is in contact 

 with the accompanying' cell (see again the emphasized cords 

 in fig. 5, pi. 91). The early stages of the transition from 

 the histologic pattern of parathyroid to the thyroid follicular 

 arrangement, or vice versa, is not difficult to comprehend 

 from the conditions present in these parathyroid sections. 



Spots of the darker staining bluish cells are seen irregu- 

 larly located near the periphery of the parathyroid from 

 620 6 and show chiefly in the left half of the photomicro- 

 graph. The parathyroid gland unquestionably presents his- 

 tologic distortions, but whether these are related in a causal 

 manner to defects in the structural constitution of the animal 

 is at present impossible to state. The teeth of this dog were 

 badly broken in places and undermined through degeneration 

 and resorption of the alveolar bone, and this might possibly 

 be associated with the parathyroid defects; but it is also 

 possible that it is a direct result of mechanical irritation 

 due to the extreme dental malocclusion which existed between 

 the structurally disharmonious jaws. The general life history 

 of the animal was normal except that it had difficulty in taking 

 food in competition with other dogs and that the many 

 attempts at breeding were unsuccessful. 



Figures 2 and 4 in plate 92 illustrate sections of the para- 

 thyroids from 524 6 and 525$. These animals were brother 

 and sister litter mates from a backcross of the F x Boston 

 terrier-dachshund with the Boston terrier parent. Photo- 

 graphs of the animals from life are shown in plate 44 (figs. 

 1 and 3) (p. 247). They resemble poor typed Boston terriers. 

 Sections of the thyroid glands from these individuals have 

 already been examined (figs. 3 and 4, pi. 86), and were de- 

 scribed as presenting an almost complete histologic pattern 

 of the thyroid distortion typical of the Boston terrier gland. 

 The pituitary glands from these two dogs were seen to be 

 cystic and abnormal (figs. 1 and 2, pi. 90), the gland from 

 524<? being more distorted than that from the sister. 



