1106 



THYROID GLAND. 



of well marked prismatic, sometimes of octo- 

 hedral, form, are seen occasionally in the 

 glandular cavities. They are generally single in 

 each, and I have no other guide than their 

 form to lead me to any opinion respecting 

 their chemical constitution. I have seen, in 

 a human thyroid, some large oval or circular 

 corpuscles about ^Vw incn diam., consisting 

 of coarse granular matter not surrounded 

 by any distinct envelope, and of an opaque 

 dead white colour. These were perhaps ab- 

 normal formations ; yet in a tortoise, where the 

 gland was quite healthy, similar corpuscles, 

 and more numerous, were observed. The 

 clear fluid material, contained within the 

 glandular cavities, is generally spoken of as of 

 an albuminous nature. This opinion seems con- 

 firmed by two analyses of the gland, made by 

 my friend Mr. Beale, which may be regarded 

 (after allowance is made for the areolar tissue, 

 vessels, envelopes, and epithelium) as express- 

 ing pretty correctly the chemical nature of the 

 secretion which forms so large a part of the 

 whole bulk. These analyses I will presently 

 quote, but will first detail a few observations 

 of my own, as to the effects of certain re- 

 agents on the fluid in question. 



Liq. Potasses, added to a thin section pre- 

 pared for the microscope, rendered it much 

 more transparent, partially dissolving the epi- 

 thelium, and leaving a quantity of oily matter 

 diffused throughout it. Acetic acid now added 

 to the specimen pretty nearly restored it to 

 its former appearance, but did not bring into 

 view any precipitated protein. Acetic acid, 

 alone, dissolves in part the epithelium of the 

 vesicles, and renders the fibrous tissue more 

 transparent. Liq. Ammonia; dissolves the 

 epithelium in great part, but does not alter 

 the transparent contents of the cavities ; nor 

 does liq. potassae or acetic acid. Solution of 

 iodine does not materially affect the epithe- 

 lium of the cavities, but renders it more 

 opaque. Strong nitric acid at first renders the 

 epithelium more opaque and granular, but does 

 not manifestly affect the contained secretion. 

 After a time it colours this material bright 

 green or yellowish green, and disengages a 

 great many bubbles of gas. A saturated 

 solution of bichloride of mercury, even after 

 long maceration, does not seem materially 

 to affect the secreted contents of the vesicles ; 

 it makes their peripheral stratum of epithelium 

 quite opaque; but the interior still appears 

 transparent and glistening. 



The chief conclusion deducible from the 

 above results is, that the secreted material of 

 the glandular cavities of the thyroid is not 

 ordinary fluid albumen ; as otherwise it would 

 certainly be coagulated by the agents em- 

 ployed. The effect produced by nitric acid is 

 also worthy of notice, though I cannot ex- 

 plain tfce meaning of it. 



Analysis of thyroid gland. 



Human. Ox. 



Water - - - 70'6 71 '34 

 Solid matter - - 29-4 28'66 



100 



100 



29-400 28-660 



The analyses given above testify to the 

 presence of a large quantity of fibrinous and 

 albuminous matters in the gland, and leave no 

 doubt that its secretion is a protein com- 

 pound ; it is, however, unfortunately impos- 

 sible to procure a sufficient quantity apart 

 from other substances to analyze correctly ; 

 and the exact nature of the thyroideal secre- 

 tion consequently still remains unknown. 

 Thus much, however, seems to be ascertained, 

 or rendered very probable. (1) That the 

 secreted material is of an albuminoid nature. 

 (2) That it is not in the state of ordinary fluid 

 albumen. (3) That gelatine is sometimes an 

 ingredient of the secretion; (it was found in the 

 gland of an ox, but not in that of the human 

 subject, and consequently could not have been 

 derived from the fibrous tissue). (4) That 

 though crystals of triple phosphate and of 

 oxalate of lime occur in the cavities, no urea 

 nor lithic acid, nor in fact any special organic 

 compound, can be detected.* 



Vessels. The vascular supply of the thy- 

 roid is very abundant, and completely justifies 

 Cruveilhier's opinion, that more than a mere 

 process of nutrition is carried on in the gland. 

 The arteries which are distributed chiefly to 

 this organ are very constant in their number, 

 and tolerably so I think in their respective 

 dimensions, though in this respect they vary 

 inversely with regard to each other. They 

 ordinarily arise, as has been well remarked by 

 Mr. Simon, just beyond the points where the 

 arteries to the brain are given off from the 

 large trunks, a circumstance which he con- 

 ceives to be very significant of the function of 

 the gland which they supply ; the two 

 superior thyroideal arising one on each side 

 from the external carotids, almost immediately 

 after the bifurcation of the common carotids, 

 and the inferior thyroideals from the intra- 

 scalenal portion of the subclavian, almost 

 opposite the point where the vertebrals are 

 given off. A fifth thyroideal artery occa- 

 sionally exists, that named after Venbauer; 

 taking its origin from the arch of the aorta or 

 thearter. innominata. The superior thyroid not 

 unfrequently takes origin a little lower down 

 from the division of the common carotid, or 

 even from its trunk ; or it may arise higher up 

 from a common trunk with the lingual. It 

 courses first forward and inward, when it is 



* I would not omit to express here my obligations 

 to Mr. Beale for undertaking the analyses, and for 

 the care and skill with which he has performed 

 them. 



