77//; Fr\(Tio\s or Tin-: Tiirnoih 591 



tivity. All these conditions are relieved to jrreater or less degree by 

 adiniiiistratioii of thyroid tissue or its preparations.'* Evidently, 

 therefore, tiie thyroid exerts an influence upon growth and tissue 

 changes ; whether this depends upon its influence upon metabolism, or 

 is an independent and specific function, cannot be determined.* 



IIow the thyroid or its secretion modifies metabolism is not yet un- 

 derstood. One is reminded of the effects of kinases upon enz^-mes 

 and their antecedents, and it may be imagined that the thyroid secre- 

 tion activates both proteolytic and oxidative enzymes vv^ithin the cells. 

 Shryver,"^ indeed, did find that administration of thyroid to dogs for 

 some time before killing them causes their liver tissue to undergo 

 autolysis more rapidly than normal, although AVells " had been unable 

 to observe any increased amount of autolysis when thyroid extracts 

 acted upon liver tissue in vitro. Experimental observations show 

 that carbohydrate metabolism is much influenced by the thyroid, so 

 that thyroidectomized animals may fail to show glyeosviria from vari- 

 ous procedures that usually produce it (King),^ and they are incapable 

 of utilizing sugar injected parenterally as well as normal animals ; ^ 

 they also exhibit an excessive creatine output, but otherwise show no 

 striking changes.'*'' 



Detoxicatory Function. — The evidence that the thyroid has for its 

 function the destruction or neutralization of poisonous substances 

 formed in metabolism or through intestinal putrefaction is as follows : 



(1) After total removal of the thyroid from many species of ani- 

 mals acute symptoms develop that suggest strongh' an intoxication. 



(2) After removal of the thyroid, marked changes occur in the 

 blood, there being a severe anemia (as low as 2,000,000 red corpus- 

 cles), Avith some leucocytosis, and there occur structural changes in 

 the blood-vessel walls (Kishi).'* Cytoplasmic degeneration of the 

 liver, kidneys, and myocardium may also result (Bensen).^'^ These 

 effects suggest strongly the presence of poisonous substances in the 

 blood of persons or animals lacking sufficient thyroid tissue. 



(3) All the effects of thyroidectomy are more marked in carnivor- 

 ous animals than in herbivora ; indeed, the latter may be able to live 



3 Concerning tlie influence of thyroid on skeletal growth see Holmgren. Xordiskt 

 Med. Arkiv, 1910 (43), No. 2. Literature given bv Basingcr, Arch. Int. 31ed., 

 1916 (17), 260. 



4 See the interesting experiments of Oudernatsch (Arch. Entwickl., 1J)12 (35), 

 457; Amer. Jour. Anat., 1014 (15), 431: Anat. Record, 1017 (11), 357), Avho 

 found that feeding thyroid to tadpoles hastens their differentiation but checks 

 growth. 



5 Jour, of Physiol., 1005 (32), 150. 



6 Amer. Jour. Phvsiol., 1004 (11), 351; corroborated by Morse, Jour. Biol. 

 Chem., 1915 (22), 125. 



7 Jour. Exper. IVled., 1000 (11), 665. 



sUnderliill and Saiki, Jour. Biol. Chem., 190S (5), 225. 

 8a Hunter, Quart. Jour. Phvsiol., 1014 (8), 23. 

 9Virchow's Arch., 1004 (176), 260. 

 loVirchow's Arch., 1902 (170). 220. 



