THE THYROID. 89 



Various attempts have been made to discover the active principle in 

 the thyroid which is responsible for its curative properties. Notkin 1 

 attributes the activity of the gland to its proteid constituents, especially 

 to the one called thyrcoproteid by Bubnow, 2 which acts after the 

 manner of an enzyme. 



Gourlay 3 made a thorough investigation of the proteids obtainable 

 from the organ. His conclusions were as follows : 



1. The only proteid that can be obtained in any quantity from the 

 thyroid is a nucleo-proteid. 4 This may be prepared by either the acetic 

 acid or sodium chloride method, and when intravascularly injected 

 causes thrombosis. 



2. This is derived, at any rate partly, from the colloid matter in the 

 acini; it yields no sugar on treatment with dilute mineral acid, and 

 is therefore not a mucin or mucoid. Moreover, the microchemical 

 method of Lilienfeld and Monti shows that it contains phosphorus. 

 The absence of mucin is confirmed by Frankel and by Hutchison. 



3. Small quantities of albumin are also obtainable. 



A year later Frankel 5 separated from the gland a crystalline 

 material, with the formula CgH^NgOg, which he called thyr co-antitoxin, 

 though the experimental and clinical evidence quoted hardly seem to 

 justify the name. 



Eoos and Baumann 6 have discovered an iodine-containing material, 

 which occurs chiefly in combination with the proteid of the organ, but 

 partly free. It is remarkable in being insoluble in 10 per cent, hydro- 

 chloric acid, a reagent which dissolves all the other substances present. 

 It was previously known that the active substance was very stable. 

 Thyroid feeding is followed by as good results as injection of thyroid 

 extracts ; the active substance therefore resists the action of digestive 

 ferments. The substance was named by its discoverers thyro-iodin, or 

 iodo-thyrin ; it contains 9'3 per cent, of iodine, and 0*56 per cent, of phos- 

 phorus. It is not probably a derivation of nuclein, but its constitution is 

 not yet known. The amount of iodine per gramme of the organ in human 

 adults varies from 0'3 to 0'9. 



Whether this substance is really the important proximate principle in 

 thyroid extracts and by inference in the normal internal secretion of the 

 organ, must still be left to the future. For, though Eoos and Baumann 

 state that it acts in every way like thyroid extracts, Gottlieb 7 has been 

 unable to confirm the statement, though possibly, as Auerbach 8 suggests, 

 this is to be attributed to his having used preparations very poor in iodine. 

 Weak points in the theory appear to be the absence of the substance 

 in the thyroids of children, and in some animals like dogs unless they 

 are put on a particular diet (dog biscuits). Small quantities of iodine 

 are found also in the thymus. 



1 Wien. med. Wchnschr., 1895, Nos. 19 and 20 ; Virchow's Archiv, 1896, Bd. cxliv. 

 S. 224. The ferment theory was also urged by White and Davies, Brit. Mcd. Journ., London, 

 1892, vol. ii. p. 966. 



2 Ztschr.f. physiol. Chem., Strassburg, Bd. viii. S. 1. 



3 Journ. Physiol. , Cambridge and London, 1894, vol. xvi. p. 23. 



4 Morkotun (Vrach, St. Petersburg, 1895, No. 37) gives the composition of this 

 nucleo-proteid as C, 51 '46 ; N, 15 '56 ; P, 0'32 ; H, 6 '94 ; S, 1'5 ; 0, 24 '22 per cent. 



5 Wien. med. BL, 1895, No. 48 ; 1896, Nos. 13, 14, and 15. 



6 Ztschr. f. physiol. Chem., Strassburg, Bd. xxi. S. 19, 319, 481 ; xxii. S. 1, 18. 



7 Deutsche med. Wchnschr., Leipzig, Bd. xxii. S. 235, 



8 Centralbl. /. Physiol., Leipzig, 1896, Bd. x. S. 133. For various other references 

 to clinical work on this question, see ibid., No. 6. For the influence of iodo-thyrin on 

 metabolism, see F. Voit, Ztschr.f. Biol , Miinchen, 1897, Bd. xxxv. S. 116. 



