THE THYROID GLAND. 183 



in the interior, are unknown. The few nerves, lastly, are only 

 vascular nerves and are derived from the cervical portions of 

 the sympathetic. 



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

 frequent degeneration of the thyroid, 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 

 hyperaemiated condition, numerous aneurismal dilatations of 

 the smaller vessels, for the most part of those 0030 — 0-040'" 

 in size, which Ecker looks upon as arteries and larger capillaries, 

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

 cysts, of various sizes, subsequently ensue, which 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 fre- 

 quently met with a cretification of the vessels, consisting 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 hypertrophy 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 Remak, the thyroid body is developed by the 

 constriction of a portion of the anterior wall of the pharynx, 

 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 0016 — 0'05'" in size, consisting 

 of a homogeneous envelope and rounded- angular cells in the 

 interior, and I think I perceived that this follicle was multi- 

 plied by the formation of rounded buds and their separation 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 



