518 



A TEXTBOOK OF PHYSIOLOGY 



this disease. By those' who believe that thyroid and parathyroid are 

 glands with different functions it is claimed that extirpation of the 

 thyroid produces symptoms akin to myxoedema, with sometimes a 



slow death ; while extirpation of the para- 

 thyroids produces the nervous symptoms 

 of tetany convulsions and a quick death. 

 The evidence in favour of and against 

 these views is very conflicting. Undoubt- 

 edly, in some cases the removal of the 

 thyroid produces the " myxcedematous," 

 and of the parathyroids the " nervous " 

 syndrome; but in some cases thyroid 

 removal produces in addition the nervous 

 symptoms, or these alone; Avhile extirpa- 

 tion of the parathyroid, instead of pro- 

 ducing the nervous symptoms of tetany. 

 calls forth " cachexia/' or deficient meta- 

 bolism of myxoedema. 



A substance rich in iodine has been 

 isolated from the thyroid, called iodo- 

 thyrin or thyreo -iodine. The active part 

 of the colloidal protein secretion of the 

 thyroid is often stated to be this sub- 

 stance. Recent evidence, hoAvever, tends 



to show that this is not the case. The true secretion passes into 

 the blood when" the* nerves (the superior laryngeal)"[to[ the gland are 



FIG. 255. A TYPICAL CASE OF 

 EXOPHTHALMIC GOITRE IN A 

 YOUNG WOMAN. 



(From " Index of Differential 

 Diagnosis," I. Wright and 



Stimulation of 

 depressor. 



A 



Stimulation of depressor 

 nerves. 



A 



Stimulation of thyroid nerves. 



FIG. 256. To SHOW THE EFFECTS OF STIMULATION OF THE DEPRESM.K NKKVK 



WITHOUT AND WITH STIMULATION OF THE NERVES (SUPERIOR LARYNo'sAL) TO 



THE THYROID. (Asher and Flack.) 



stimulated, as is demonstrated by the fact that certain actions are 

 augmented by this, just as they are by an intravenous injection of 



