SEC. 5. ON SOME STRUCTURES AND PROCESSES OF 



OBSCURE NATURE. 



§ 392. The Thyroid Body. Certain structures which, 

 though they differ in many ways, we may conveniently treat of 

 together, such as the thyroid and pituitary bodies, the supra- 

 renal capsules, and the thymus, appear to play not unimportant 

 parts in the metabolic processes of the body. 



In regard to the thyroid we have clinical and experimental 

 evidence pointing distinctly in this direction. In certain animals 

 (such as monkeys and dogs) the removal of the thyroid gives 

 rise to various symptoms of disorder. Among the earlier of 

 these are muscular tremors, spasms or even tetanic convulsions, 

 accompanied or succeeded by irregularity or failure of voluntary 

 movements, all indicating mischief in the central nervous 

 system, in which indeed histological changes may be detected. 

 Subsequently there ensue other varied symptoms which may be 

 described under the general term of those of disordered nutri- 

 tion, and which eventually end in death. In order to obtain 

 these results the whole of the thyroid gland, including the 

 small so-called accessory thyroids, when these are present, must 

 be removed; if a part only of the body be left behind the 

 symptoms do not appear, or are slight and transient. Mere 

 injury either to the thyroid body itself, or to the surrounding 

 nervous and other structures, is insufficient to produce the 

 characteristic results. Moreover, if the thyroid, after the 

 removal from its natural position and attachment, be inserted as 

 a whole or in part in some other part of the body, so as to live 

 and thus be "grafted," the symptoms do not appear. The 

 story in fact is very similar to that of the pancreas in relation to 

 sugar in the blood (see § 374). And we may infer that in these 

 animals the blood in passing through the thyroid undergoes 

 some special change, some thing or things being taken away 

 from it or added to it, by which it is fitted for the nutrition of 

 the rest of or at least of other parts of the body. We may add 

 that in other animals, herbivora for instance, these symptoms 

 are not so easily produced. The reason may be the greater 



000 



