972 



SCIENCE. 



[N. S. Vol. V. No. 130. 



sible to draw certain definite conclusions. 

 In the first place it must be remembered 

 that the epithelial cells of the thyroid gland 

 apparently manufacture a so-called colloid 

 secretion which evidently finds its way into 

 the blood through the lymph, presumably 

 carrying with it the active principles. This 

 secretion obviously cannot be collected for 

 study, but such active principles as it 

 contains may be sought for in the gland 

 itself^ since we have eveiy reason to 

 believe in their ready solubility. By his- 

 tological methods applied to sections of the 

 thyroid it has been shown that the colloid 

 matter gives the general proteid reactions, 

 that it is very soluble in dilute alkaline 

 fluids and readily dissolved by gastric 

 digestion.* Our knowledge of the chemical 

 composition of the thyroid gland, and hence 

 presumably of the colloid secretion, is due 

 mainly to the work of Bubnow,t Gour]ay,:|; 

 ]S'otkin,§ Moscatelli,|| Frankel,^ and es- 

 pecially Baumann and Eoos,** and Hutch- 

 inson .ft To briefly summarize the present 

 state of our knowledge, ignoring minor 

 points of difierence, I think it is quite clear 

 that the thyroid gland Is especially charac- 



*LaDgenclorff ; Beitragr zur Kenntniss der Sohild- 

 driise. Du Bois-Eeymonds Archiv f. Physiol., 1889, 

 Supplementlieft, p. 219. 



fBeitrag zur d. TJntersuchung der ohemischen 

 Bestandtheile der Schilddriise des Menselien und des 

 Rindes. Zeitsohr. f. Physiol. Chem., Band 8, p. I. 



JThe Proteids of the Thyroid and the Spleen. 

 Journal of Physiol., Vol. 16, p. 23. 



^Zur Schilddriisen-Physiologie. Virchows Arohiv. 

 Band 114. Supplementheft, p. 224. 



||Beitrage zur Kenntniss der Milchsiiure in der 

 Thymus und Thyreoidea. Zeitsohr. f. physiol. chem. 

 Band 12, p. 416. 



TfThyreoantitoxin, der physiologisoh -wirksame 

 Bestandtheile der Thyreoidea, Wiener klin. Woch- 

 enschr., 1895, No. 48. 



**Ueber das normale Vorkommen des Jods im 

 Thierkorper. Zeitsohr. f. physiol. Chem. Band 21, 

 p. 319 and 481. Band 22, p. 1. 



tfThe Chemistry of the Thyroid Gland and the na- 

 ture of its active constituent. Journal of Physiol. 

 Vol. 20. p. 474. 



terized by the presence of a compound 

 proteid of peculiar constitution, aud that 

 this substance which Hutchinson calls 

 ' colloid matter ' is the active constituent 

 of the gland. There is also present another 

 proteid, a nucleoalbumin, in small amount, 

 which Hutchinson considers as probably 

 contained in the cells of the acini. In 

 addition there are certain extractives to be 

 found, viz., xanthin, hypoxanthin, inosite,* 

 volatile fatty acids, paralactic acid, suc- 

 cinic acid and calcium oxalate ; bodies, how- 

 ever, of no special physiological signifi- 

 cance. 



The chief interest centers around the 

 above mentioned proteid material, which is 

 plainly of a peculiar kind, since it tends to 

 hold a certain amount of iodine in combi- 

 nation and yields on decomposition a pecu- 

 liar non-proteid substance carrying with it 

 most, if not all, of the iodine and endowed 

 with marked physiological action. This 

 latter substance, to which Baumann has 

 given the name of thyroiodin, later changed 

 to iodothyrin, is especially characterized, 

 chemically, by its great resistance to 

 ordinary decomposing agents. Digestion 

 of the thyroid gland with active gastric 

 juice yields the iodothyrin as an insoluble 

 residue, but still active. The gland can 

 even be boiled an entire daj' with ten per 

 cent, sulphuric acid without loss of the ac- 

 tive principle, the latter separating from the 

 cooled fluid as a fine flocculent precipitate 

 almost wholly insoluble in cold water and 

 acid, soluble in hot alcohol and readily 

 soluble in dilute alkalies. "When purified 

 by repeated precipitation, re-solution, etc., 

 the body may contain as much as ten per 

 cent, of iodine. In the gland, according to 

 Baumann, iodothyrin exists in great part 

 combined with albumin and in smaller 

 amount with globulin, and these com- 

 pounds are likewise physiologically active, 

 *Tamhaoh. Pharmaceutische Centralhalle, March, 

 1896. 



