596 CHEMICAL PATHOLOGY OF THE DUCTLESS GLAyOS 



which is the best of evidence that the formation of this compound is 

 one of the chief functions of the gland, and that the iodin in the thy- 

 roid is not merely stored there as an undesirable foreign substance 

 like copper in the liver. The selective deposition of iodin in the thy- 

 roid is remarkable, and when iodin is fed to animals it is stored very 

 rapidlj' in the thyroid, bvit it seems to require several hours before the 

 active growth-modifying hormone is formed.-^" INIarine and Lenhart -^ 

 find that the normal human gland contains an average of 0.4 mg. of 

 iodin per gram of fresh weight (2.17 mg. per gram of dry weight), be- 

 ing less than that of domestic animals in the same part of the country. 

 These figures agree closely with tliose obtained in thyroids from various 

 parts of America by Wells--' (2.10 mg. per gram dry weight). They 

 found, as Oswald and Kocher also have, that the amount of iodin varies 

 directly with the amount of colloid, being decreased when cellular hy- 

 perplasia is present, in direct proportion to the amount of hyper- 

 plasia, and administration of iodin causes a reduction in the In'per- 

 plasia and a return to the colloid type of gland, while the iodin is de- 

 posited in the gland. Kocher, however, disputes the regularity of the 

 variation of iodin and colloid content, stating that it is especially the 

 concentrated follicle contents which hold the iodin. Seidell and Fen- 

 ger ^° have found a marked seasonal variation in the thyroid iodin of 

 animals, there being about three times as much between June and No- 

 vember as between December and May.""'' In man it has been found 

 that before birth the thyroid of the fetus contains little or no iodin, 

 but in domestic animals the fetal glands contain not a little iodin 

 (Fenger).^^ The cells of the gland contain very little iodin (A. 

 Kocher). Extracts of the thyroid have little effect on the blood pres- 

 sure, except for an alcohol-soluble fraction, poor in iodin, which is a 

 depressor.^^^ 



Wasting diseases are associated with a considerable decrease in the 

 size of the thyroid and the amount of colloid, and with this a decrease 

 in the iodin ; especially is this true of tuberculosis.^- Patients or ani- 

 mals to whom iodin compounds are administered deposit it in the 

 thyroid in large amounts, especially if the gland is previously de- 

 fective in iodin, and at times there results even an acute thyroiditis 

 from the iodin administration.^^ Iodides are said to increase the 



340; Hunt. Jour. Amer. Med. Assoc, 1907 (49), 1323; and Jour. Pharm. and oxp. 

 Therap., 1910 (2), 15. 



27a Marine and l^ogofi", Jour. Pliarm., 191G (9), 1. 



28 Arch. Int. Med., 1909 (4), 440. 



29 Jour. Amer. :Med. Assw., 1897 (29), 897. 



30 .Tour. P.iol. Clieni., 1913 (13), r,]l. 



30a \'alual)k' fifjures on tlic iodin content of foods are given bv Forhes ct at., 

 Bullet. Oliio Agric. Exi)t. Stotion, June, 1910. No. 299. 



31 Jour. Piol. Cliem., 1912 (11), 489; 1912 (12), .5;); 1913 (14), 397. 

 3ia Fawcett et al., Amer. .Four. Pliysiol., 1915 (.3(5), 113. 



32 See Vitrev and Hiraud, Conijjt.'Rend. Soc. Biol., 1908 (65), 405. 



33 See Mendel, .Med. Klinik, 19()(; (2), 833. 



