454 CHARLES ft. STOCKARD AND E. M. VICARI 



may occur in specimens from this breed. Figure 3 shows, 

 in the mid-ventral portion of the pars distalis, a super- 

 ficially placed epithelial cyst filled with mucoid substance. 

 This cyst is lined by low non-ciliated cuboidal cells. As we 

 shall see beyond, these anterior pituitary cysts are quite 

 common in many of the dog breeds, and we have much evi- 

 dence that they are definite embryonic arrests. In exaggerated 

 cases, the cysts are lined with ciliated columnar epithelium 

 and show types of mucous cells much like those of the early 

 stomodeal lining from which they came. Tracing through 

 serial sections, we find that the large cysts almost invariably 

 extend toward the pars tuberalis in a peripheral direction, 

 an indication of their early connection with the hypophyseal 

 stalk. In other cases the proximal ends of the cysts become 

 cord-like or almost completely lost, and the cyst itself may 

 lie far from its early connections. Such cysts, however, are 

 peripheral rather than central in position, and are lined with 

 cells of less primitive embryonic type. The cyst in figure 3 

 is of this detached and rather benign nature, and this is also 

 the case with the only two other small cysts which have been 

 found in pituitaries from seven prize typed dachshunds. These 

 cysts were all lined with low cuboidal non-ciliated epithelium. 

 In contrast with many of the pituitary cysts found in other 

 breeds, the quality of the dachshund pituitary cyst is inter- 

 preted to mean that the influences causing the embryonic 

 arrest occurred rather early in the development of the pi- 

 tuitary and then ceased to act, thus not interfering with the 

 later development and differentiation of the gland. The cysts, 

 nevertheless, remain as evidence that there was a moment 

 during pituitary development when differentiation was not 

 progressing properly. 



Other features of the photomicrograph (fig. 3) are quite 

 normal except that the vessels are seen to be gorged with 

 blood due to congestion at the time of death. The animal 

 from which this gland was taken was a typical specimen of 

 the breed and is shown from life as figure 1 in plate 29 (p. 



