456 NELSON W. JANNEY 



count of its porosity to water. The greater incidence among farm workers 

 and miners, is explained by their contact with infected soil. (Mac- 



Kenzie. ) 



McCarrison emphasizes that water pollution per se is not the cause 

 of infection, but just as in the case of typhoid fever, water pollution plus 

 the specific excitant of the disease, i. e., fecal bacteria and their toxins. 



The greater prevalence of the disease in marshy regions is ascribed 

 to the greater danger of infection through infected water ever present in 

 these areas. According to this view drainage of swampy endemic districts 

 should be followed by a decrease in goiter and cretinism. Such observa- 

 tions, it may be incidentally remarked, have actually been recorded by 

 St. Lager and others. 



The relation of a contaminated water supply to the production of goiter 

 in brook trout has been studied by Marine and Lenhart (e) and Gaylord. 

 The fish were confined in a series of tanks placed one above the other 

 in a flowing stream harboring normal trout above and below the laboratory 

 station. Stagnant water and unclean tanks produced thyroid hyperplasias 

 among the confined trout in direct ratio to the amount of impurities pres- 

 ent. Thus 84 per cent of the fish in the lowermost tank developed goiter 

 under these circumstances, while the upper tank showed but 3 per cent 

 of thyroid hyperplasias. The addition of iodin, mercuric chlorid or arsenic 

 in small amounts, to the water in the tanks, cleaning the same, or the intro- 

 duction of fresh water led to a decrease in the goitrous tendency. Gay- 

 lord administered scraping from the fish tanks to dogs and rats which 

 developed goiters. Boiling* rendered this material innocuous. 



McCarrison (c) has aptly applied these data in conclusions drawn from 

 study of endemic erethism in the Indian villages along the Gilgit-Fan 

 Kiver, remarking that the incidence of the disease regularly increased 

 from 12 per cent of the total population in the uppermost to 46 per 

 cent in the lowermost village, which received the accumulated drainage 

 from the six communities lying above it. 



McCarrison likewise carried out a number of therapeutic experiments 

 which tend to boar out his contention for the intestinal origin of the dis- 

 ease. Agents such as thymol and other intestinal antiseptics, composite 

 vaccines prepared from intestinal bacteria of goitrous individuals, similar 

 auto-vaccines, or staphylococcus vaccine, lead in many instances to decrease 

 in, or in favorable cases to a disappearance of, the goiters. 



The relation of the thyroid to the infectious etiology of endemic cre- 

 tinism is regarded by McCarrison as an indirect one. In addition to its 

 control of growth and metabolism the thyroid functions in combating tox- 

 emia from intestinal and other causes. In the event of the specific excitants 

 <>l the disease boin- present there is greater need of functional activity, 

 together with an actual injury of the thyroid tissue. For these reasons, 

 hypertrophy ensues, which is indirectly but favorably influenced by the 



