520 



THYROID. 



[CHAP. xxxv. 



sent. In most instances, the vesicle can be seen to be lined with 

 a single layer of this epithelium, and many free cells are usually 

 found floating in the fluid contained in the cavity. 



The fluid in the vesicles is coagulated by heat and nitric acid, 

 and evidently contains a large quantity of albumen. 



The stroma of the gland consists of fibres of both the white and 

 yellow element, and it supports the blood-vessels, which are exceed- 

 ingly numerous, and form a capillary plexus round each vesicle. 



The lymphatics in the thyroid are numerous, but of their ulti- 

 mate distribution nothing is known. 



The following are analyses of the thyroid body, by Dr. Beale.* 



Water . 

 Solid matter . 



Human. Ox. 



70-60 71-34 

 29-40 28-66 



Fibrinous and albuminous matter, vessels, and 



fat . . . -- . - . . . . 26-384 24-628 



Extractive matter . . . ..: ;.,;.-.. . 1-70 



Extractive matter, with gelatine ... 2-888 



Alkaline salts . . . . V *,, , ' 50 ' 642 



Earthy salts . . . .'. .^ .' . '816 -502 



Uses of the Thyroid. Of the uses of the thyroid but little is 

 known. The material found in the vesicles is of an albuminous 

 nature. Mr. Simon has advanced the opinion that the thyroid acts 

 as a diverticulum to the cerebral circulation, and that its nutrition 

 bears a certain relation to that of the nervous matter of the brain. 

 When the latter is quiescent, the thyroid is supposed to be active 

 in removing from the blood, and storing up in its cells, certain 

 constituents which are required by the brain only in its active 

 state, and which are diverted to it when it resumes its activity. 

 This view is based upon the important fact, that the arteries of the 

 thyroid body arise in close proximity to those which supply the 

 brain, the superior thyroids coming off from the external carotid, 

 just immediately above the point of bifurcation of the common 

 carotid, and the inferior thyroid arteries, from the subclavian, al- 

 most immediately opposite the origin of the vertebrals. 



Thymus. The thymus body or gland is an organ only dis- 

 tinctly recognisable during early life. It appears to reach its 

 largest size between the first and third years ; but much variation 

 occurs in this point in different individuals. It lies partly in the 

 thorax and partly in the neck, and is composed of two lobes, which 



* Dr. Handfield Jones, article " Thyroid," Cyclopaedia of Anatomy and 

 Physiology. 





