.1/ yxKDi: 1/ 1 \\i) ('inrri \ is 1/ . 601 



it is of ail al)ii(»rinal nature that ])i'events its eluMiiical coinbiuatioii 

 with iodin.''" Possibly this explains the greater iodiii content ob- 

 served in colh)id goiters in the United States as compared with eoUoid 

 goiters observed in goitrous districts. In general, Oswald "" found 

 the amount of iodin to vary with the amount of colloid in the goiters, 

 although occasionally goiters with exceptionally large amounts of iodin 

 were found, and the proportion of iodin is not usually so great when 

 the amount of colloid is very large. Simple hj'perplastic goiters he 

 found i)oor in iodin, or free from it if they contained no colloid; 

 however, they were found to contain a thyreoglobulin tyjiical in all 

 respects except an absence of iodin. Presumably in such goiters the 

 little thyroiodin present is contained in the parenchymatous cells. 

 The physiological activity of thyreoglobulin obtained from goiters was 

 found to be the same as that from normal glands, exce])t that it was 

 weaker in direct proportion to the amount of iodin it contained, and, 

 therefore, when iodin-free it w^as without effect. In colloid goiters 

 the greater part of the weight of the gland, three-fourths or more, is 

 made up of this colloid-poor thyreoglobulin. The fluid contents of 

 cystic goiters may be free from iodin, but if they contain much colloid, 

 iodin will be found, and Rositzky "^ found 0.193 mg. of iodin in 20 c.c. 

 of the jelly-like contents of a thyroid cyst. 



It has been frequently suggested that the cause of endemic goiter 

 is a deficiency in the iodin in the food, or in the drinking-water, or in 

 the air of the goitrous district. This is supported by the relative in- 

 frequency of endemic goiter in districts on the sea-coasts, where the 

 iodin-containing sea-water is sprayed through the air, and where the 

 inhabitants eat largely of sea-foods. However, there are many ex- 

 ceptions, and it cannot be said that this hypothesis of the etiology of 

 goiter rests on satisfactory evidence, particularly in view of the abun- 

 dant iodin content of colloid goiters. Epidemics of goiter presuma- 

 bly are the results of an infection with some unknown organism, and 

 possibly the endemic form has a similar cause. There is much evi- 

 dence, in any event, that whatever the cause of goiter may be, it often 

 is related to the drinking water,*'- but numerous well-controlled experi- 

 ments fail to support this hypothesis."-'' Very probably the causes 

 of colloid goiter and parenchymatous goiter will be found to be differ- 

 ent from the causes of cystic and adenomatous goiters. 



MYXEDEMA AND CRETINISM 



These conditions depend upon a deficiency of thyroid secretion, 

 whether from operative procedure or from pathological alterations m 



59 See Kooher, ]\ritt. a. d. Grenzfreb. Med. u. Chir., 1905. vol. 14. 



coVirchow's Aroli.. l!in-2 (16!)), 444. 



ei.Wien. klin. Woeli., 1807 (10), 82.3. 



fi2 See de Quervain, ]\Iitt. a. d. Grenzgcb. ^Icd. n. Chir., IDOo (lo), 207 : Birchcr, 

 Zeit. exp. Path. u. Ther., 1911 (9), 1. 



62a See Munch, med. Woeh., 191.3 (60), 393 and 1813: Sitzber. ^Yion. Akad., 1914 

 (123), 35. 



