CHEMISTRY OF TlIK THYROID 599 



(4) Reid Hunt'' found tliiit mice fed thyroid preparations have a greatly in- 

 creased resistance to poisoning l)yaceto-nitrile; however, this is not necessarily nor 

 even probably a direct detoxication, but more likely it results from alterations in 

 metabolism.'" Rats and Ruinca pigs behave just the opposite, showing a decreased 

 resistance to acetonitrile after being fed thyroid, and according to some authors 

 morphine is more toxic for such animals." 



Whether the thyroid exercises its detoxicating effect, assuming that 

 it has one, by a direct neutrahzing action of its secretion upon the 

 to.xic substances in the blood or in diver.se tissues, or indirectly by 

 stimulation of the function of other tissues which perform the detoxica- 

 tion, or in part locally within the gland itself, is an unsettled problem. 

 In relation to the last-named hypothesis is the extreme vascularity 

 of the thyroid, which, according to Burton-Opitz-" has passed through 

 it much more blood in proportion to its weight than any other gland. 

 Against the idea of a local detoxication is the fact that after extirpation 

 of the thyroid all abnormal conditions may be prevented by proper 

 administration of thyroid substance. 



Biedl summarizes his views as to the function of the thjToid, in 

 the following statement: "The thyroid is a secretory organ which 

 discharges its secretion eventually into the blood, in the form of an 

 iodin-containing protein. This secretion acts as a hormone, in that 

 it modifies the activities of remote tissues. As far as we now know 

 the thyroid secretion plays the role of a 'disassimilatory' hormone, in 

 that it causes an increased disassimilation and increase of normal activ- 

 ity in many tissues. This effect is exemplified by the augmented 

 metabolism, the activity of the heart and many parts of the sympa- 

 thetic nervous system, and of a series of internal secretory organs 

 (adrenals, hypophysis). In other tissues are found evidence of the 

 action of an inhibiting and assimilatory hormone, as shown in the in- 

 crease in growth of bone, development of the sex glands, and decreased 

 internal secretion of the pancreas." 



Chemistry of the Thyroid^' 



Whether the function of the thyroid is the neutralization of toxic 

 substances, or a complementary action upon intracellular metabolism, 

 there can be little question that it owes its action to constituents of 

 its specific secretion, the colloid.-- Furthermore, the chief, if not the 

 sole, active ingredient of the colloid is the iodin-containing substance 



I'' Jour. .\mer. Med. Assoc, 1907 (49), 240; Hygienic Lab. BuU., 1909, No. 47; 

 Jour. Pharmacol., 1910 (2), 15. 



1* Koopman (Endocrinology, 1919 (3), 318) states that administration of 

 thyroid increases antibody formation in immunized animals. 



19 See Olds, Amer. Jour. Phvsiol., 1910 (26), 354. 



-0 Quart. Jour. Physiol., 1910 (3), 297. 



21 Reviews are given by Rahel Hirsch, Handb. d. Biochem., 1909, III (i), 

 271; and A. Kocher, Virchow's Arch., 1912 (208), 86. 



-- Beyond the characteristic colloid secretion product, the thyroid presents no 

 chemical features of interest; it differs from the other endocrine glands in being 

 poor in lipoids (Fenger, Jour. Biol.JChem., 1916 (27),',303). , 



