588 SPECIAL HISTOLOGY. 



Ecker distinguishes the struma, which is by far the most frequent 

 degeneration of the thj^roid, into a vascular and a glandular. In the 

 latter, the above-described changes of the gland-vesicles take place, 

 "whilst in the vascular struma, which is not regarded by Rokitansky as 

 a special form, besides a hypersemiated condition, numerous aneurismal 

 dilatations of the smaller vessels, for the most part of those 0-030-0-040 

 of a line in size, which Ecker looks upon as arteries and larger capilla- 

 ries, are met with. From the bursting of these dilatations, apoplectic 

 cysts, of various sizes, subsequently ensue, wliich may exhibit phases of 

 the most various kinds, as the blood undergoes changes of one kind or 

 another ; fresh extravasations, and also exudations, are superadded, and 

 even normal tissue becomes involved in them. In vascular struma, 

 Ecker also very frequently met with a cretijication of the vessels, con- 

 sisting in the deposition of numerous scattered calcareous particles in 

 the walls of the smaller and smallest, dilated or normal vessels, so that 

 they appeared quite white ; and when the affection had advanced to the 

 highest stage, were obliterated and became concretions. In a certain 

 form of scrofula, Rokitansky describes an liypertrophy of the thyroid 

 gland, due to a multiplication of the normal glandular elements, taking 

 place by the production of new gland-vesicles, sometimes independent, 

 sometimes occurring in enlarged gland-vesicles, in growths inwards of 

 their walls. 



According to Reraak, the thyroid body is developed by the constric- 

 tion of a portion of the anterior wall of the pliarynx, and the division 

 of this into two halves. In a human embryo, at the third month, I 

 found that the thyroid body was already composed of isolated vesicles 

 0"01G-0'05 of a line in size, consisting of a homogeneous envelop and 

 rounded-angular cells in the interior, and I think I perceived that this 

 follicle was multiplied by the formation of rounded buds and their sepa- 

 ration by constriction. If this really be the case, the entire develop- 

 ment, probably, of the thyroid gland would have to be regarded as a 

 continued growth and division of the glandular follicles, of which the 

 fission of the primary vesicular rudiment, observed by Remak, would be 

 merely the first phase. In this respect, also, a certain resemblance 

 with the thymus would be established, only that in the latter, both the 

 buds of the primary rudiment, as well as the later ones, are not de- 

 tached, but all remain in connection. The follicles of the thyroid 

 gland, therefore, would not be any kind of enlarged cells, and still less 

 metamorphosed nuclei (Rokitansky), but be equivalent to true gland- 

 follicles. 



The investigation of the vesicles of the thyroid gland has mainly been 

 pursued in animals, especially in Birds, Amphibia, and in children; 

 and sections obtained by means of the double-bladed knife, or glands 

 that have been hardened, are most suitable for the purpose of studying 



