PATHOLOGICAL ANATOMY AND HISTOLOGY 571 



the many changes which the thyroid adopts in its protean morphology. 

 The extrathyroid tumors of the parathyroid origin can be recognized 

 with greater certainty than those which occur in the thyroid tissues, and 

 it is the former group upon which most tress must be laid. The clear 

 differentiation between adenomatous hyperplasia and true neoplastic 

 adenoma presents much greater difficulty. In this we have a problem 

 somewhat similar to that observed in the pituitary, where all gradations 

 between a general overgrowth of the glandular elements in a process of 

 hyperplasia, and a circumscribed nodule receiving the name of adenoma, 

 occur. When such masses become of considerable size, they cause second- 

 ary distortions within the gland and its surroundings. A line of demar- 

 cation between such hyperplasia and true adenoma, can hardly be made. 

 This is also true for the parathyroids, although in these glandules circum- 

 scribed areas of adenomata are at -times found separated from a small 

 portion of remaining normal parathyroid tissue. 



The following tumorous masses, as outlined below, have been described 

 as of parathyroid origin. , 



In 1906 Askanazy (b) reported an adenoma, of the parathyroid as did 

 Verbitz. The case of Yerbitz presented the characteristics of diffused 

 adenomata. A year later, in 1907, Langhans (&) reported nine cases, five 

 of which were previously described by Kocher as parastruma. There are 

 some of these cases which cannot, however, be accepted unreservedly as 



