52 INTERNAL SECRETION 



authors found in a dog thirty days after total parathyroidectomy. 

 This gland also contained irregular vesicles, together with an 

 increase in the quantity of intravesicular tissue. The clinical 

 course of this experiment is interesting. After removal of the 

 last hypertrophied parathyroid gland, the animal lived for forty- 

 four days; it did not show any symptoms of tetany, but there 

 were trophic disturbances, such as falling of the hair, eczema 

 and idiocy. It is probable that this animal possessed accessory 

 parathyroid glands. 



The occasional occurrence of gland-like hollow spaces in the 

 parathyroids has been frequently described. These hollows are 

 lined with epithelium ; they are sometimes empty and sometimes , 

 filled with a homogeneous mass believed to be colloid. 



I have found in numerous cases that removal of the thyroid, 

 together with the internal parathyroids, is nearly always followed 

 by hypertrophy of the external parathyroids. The hypertrophy is 

 more or less clearly marked according to the length of time 

 after operation. Many authors (Walbaum, Erdheim, Pepere) have 

 failed to observe an appreciable increase in the volume of the 

 parathyroids embedded in the thyroid, after extirpation of the 

 two external glands. But Haberfeld and Schilder have recently 

 shown that the internal parathyroid glands of rabbits show a 

 very high degree of vicarious hypertrophy if, in addition to the 

 external parathyroids, the accessory glands situated in the thymus 

 are also removed. 



I found that the parathyroids of a growing dog, from which 

 the thyroid had been removed, were at the end of a year twice as 

 large as those of control animals taken from the same litter. 

 Hypertrophy of the parathyroids is by no means always 

 associated with important structural changes, although gland-like 

 hollows filled with colloid are of decidedly more frequent 

 occurrence in hypertrophied than in normal parathyroid glands. 

 Whether or not this colloid formation is a compensatory secretory 

 process which is set up in the gland after the suppression of the 

 thyroid, is at present unknown. It suggests, however, that there 

 may be a functional relationship between the two organs. 



That there is a relationship between the thyroid and the 

 parathyroid glands is suggested by the fact that hypertrophy of 

 the thyroid gland has been frequently (W. Edmunds, Lusena, 

 Vassale and Generali, Halpenny, and Thompson) observed after 

 removal of the parathyroids. The tissue changes in these 

 hypertrophied organs consist in a new formation of intravesicular 

 tissue, which either forms solid cell rows or causes irregularity irr 

 the shape of the follicles. There is also a wasting away of the 

 colloid, together with vacuolization of the contents of the follicles.. 



These changes are difficult of interpretation, but the examina- 

 tion of a large number of thyroids shows that many apparently 

 normal glands present a similar picture. Vassale thinks that 



