THE THYROID. 89 
Various attempts have been made to discover the active principle in 
the thyroid which ia responsible for its curative properties. Notion 1 
attributes the activity of the gland to its proteid constituents, especially 
to the one called thyreoproteid 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 thai can be obtained in any quantity from the 
thyroid is a nucleo-proteid. 4 This may lie 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 (_', ; H n X :i 5 , which he called thyreo-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 03 per cent, of iodine, and - 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 03 to 09. 
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 clogs unless they 
are put on a particular diet (dog biscuits). Small quantities of iodine 
are found also in the thymus. 
1 Wien. vied. Wehnsehr., 1895, Xos. 19 and 20; VircJww's Archiv, 1896, Bd. cxliv. 
S. 224. The ferment theory was also urged by White and Davies, Brit. Med. 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, Xo. 37) gives the composition of this 
nucleo-proteid as— C, 51-46 : X, 15 "56 : P, 0'32 ; H, 6*94 ; S, 1*5 ; 0, 24-22 per cent. 
5 Wien. Tried. BL, 1895, Xo. 48 ; 1896, Xos. 13, 14, and 15. 
s Ztschr. f. physiol. Chem., Strassburg, Bd. xxi. S. 19, 319, 481 ; xxii. S. 1. 18. 
'Deutsche med. Wehnsehr., Leipzig, Bd. xxii. S. 235, 
8 Ccntralbl. f. Physiol., Leipzig, 1896, Bd. x. S. 133. For various other references 
to clinical work on this question, see ibid., Xo. 6. For the influence of iodo-thyrin on 
metabolism, see F. Voit, Ztschr.f. Biol , Miinchen, 1897, Bd. xxxv. S. 116. 
