THYROID GLAND. 



1117 



impetus of the current of blood, and being 

 thus enlarged and distended, have pressed 

 upon the essential structure of the gland, and 

 caused it to become atrophied. 



It may not be amiss to observe, after this 

 review, that the disease of the thyroid, which 

 is of by far the most frequent occurrence, viz. 

 enlargement of its magnitude from excessive 

 or perverted secretory action, is just of the 

 kind we should, from our knowledge of its 

 actual structure, expect would be most liable 

 to occur. For when once the nicely arranged 

 balance of secretion and absorption, with its 

 moderate alternating oscillations in either 

 direction, is permanently deranged, the closed 

 cavities of the glandular vesicles afford no 

 exit to the accumulating matters. Thus does 

 minute anatomy explain, and thus is it con- 

 firmed by, the changes wrought by disease. 



HISTORY OF INVESTIGATIONS. The fol- 

 lowing is not presented as a complete history 

 of the thyroid, but as a sketch which it is 

 hoped contains the principal facts relative to 

 the advance of our knowledge respecting it. 



In examining the works of Aristotle, I find 

 he makes no mention of the thyroid in two 

 places, where he describes the organs situated 

 in the neck, and speaks especially of the 

 trachea. Galen does not give any very dis- 

 tinct account of the thyroid, so far as I have 

 been able to discover ; but certainly seems to 

 allude to it in a passage in his book " On the 

 Use of the Parts of the Human Body," where 

 he speaks of the glands of the larynx, " which 

 are always found more loose and spongy than 

 others, and which, by the common consent of 

 anatomists have been created for the purpose 

 of moistening and bathing all the parts of the 

 larynx and the passage of the throat." The 

 following passage, quoted also in a note by 

 Morgagni *, seems to prove that he was aware 

 of the main peculiarity of the thyroid. 

 *' Now the neck has two glands, in which a 

 moisture is generated. But from the two 

 glands which are in the neck there come forth 

 no vessels by which the moisture may flow 

 out, as those do from the glands of the tongue." 

 Vesalius, who wrote about A.D. 1542, dis- 

 tinctly recognises the existence of the thyroid 

 in the following passage from his work, " De 

 corporis humani fabrica." -|- "And this dissec- 

 tion also shows two glands, adhering one on 

 each side, to the root of the larynx, which are 

 of large size, and very fungous, and nearly of the 

 colour of flesh, but darker, and covered over 

 with very conspicuous vessels." In the second 

 book he describes their appearance in oxen, in 

 whom they resemble muscular tissue, he says, 

 very much, while in man their aspect is more 

 truly glandular. Jacobus Sylvius, who wrote 

 a little later than Vesalius, enumerates, in his 

 list of glands, " duos item ad laryngis radicem 

 asperaeque arteriae initium utrinque una quae 

 interdum ob magnitudinem in unam abire 

 videntur." Wharton, in his Adenographia, 

 published about 1656, gives a very full and 

 good description of the thyroid ; he notices 



* Advers. Anat. i. c. 26. 



f Lib. vi. cap. 4. 



its situation, figure, magnitude, texture (sub- 

 stantiam), and consistence (soliditatem) ; and 

 remarks " that it is much more full of blood 

 than any other gland, also more viscid and solid, 

 and more resembling muscular flesh. This 

 is the only difference, that it is not of a fibrous 

 structure, but rather of a glutinous nature.'* 

 He assigns four uses to the gland, which it 

 may be worth while to quote, as affording an 

 example of the speculations then in vogue, 

 the last perhaps being not the least real and 

 important of those he mentions! "(1) The 

 first and principal use of these glands appears 

 to be to take up certain superfluous moistures 

 from the recurrent nerve, and to bring them 

 back again into the vascular system by their 

 own lymph channels. (2) To cherish the 

 cartilages to which it is fixed, which are rather 

 of a chilly nature, by its own heat ; for it is 

 copiously supplied with arteries, and abounds 

 with blood, from whence it may conveniently 

 impart heat to the neighbouring parts. (3) 

 To conduce by its exhalations to the lubri- 

 cation of the larynx, and so to render the 

 voice smoother, more melodious, and sweeter. 

 (4) To contribute much to the rounded con- 

 tour and beauty of the neck ; for they fill up 

 the empty spaces about the larynx, and make 

 its protuberant parts almost to subside and 

 become smooth, especially in the female sex, 

 to whom on this account a larger gland has 

 been assigned, which renders their necks more 

 even and beautiful." 



Verheyen, writing about 1720, describes 

 the thyroid as deriving its name from the 

 cartilage so called, and states that it is con- 

 sidered by some as double, i. e. consisting of 

 two glands. He says, "this gland, beyond 

 doubt, serves also to moisten the neighbour- 

 ing parts ; but, because it is very large, there 

 is an apparent reason why it should have 

 rather large excretory ducts, or one at least 

 very conspicuous, which yet hitherto has not 

 been discovered." 



About 1708, Evertzen wrote an inaugural 

 dissertation on the thyroid gland, noticing its 

 structure, some diseases to which it is liable, 

 and their treatment. 



Morgagni, in his Advers. Anat. (1723) dis- 

 cusses two questions respecting the thyroid ; 

 one as to whether the gland is double or 

 single, i. e. whether the lobes are connected 

 by an isthmus or not ; this he decides, as re- 

 spects man, positively in the affirmative. The 

 other vexata questio, as to whether the thyroid 

 be provided with a duct or not, he confesses 

 to be yet undetermined. He notices the ex- 

 istence of vesicular cavities in enlarged thy- 

 roids, which he justly supposes to be the 

 natural cavities (nativi acini) dilated by their 

 accumulated secretion. From his examina- 

 tion of the secretion of the thyroid, " mollem 

 quendam, et obliniendo lubricandoque ido- 

 neum, succum communi isti amygdalarum 

 oleo longe consimilem;" and from observing 

 the thyroid to be exposed to the pressure of 

 contracting muscles, as is the case with some 

 other undoubted glands, he inclines to con- 

 sider it probable that the gland has some duct 



