326 On the Experimental Production of Congenital Goitre. 



animals live. The infection is conveyed from one animal to another by some 

 indirect means and not directly, as by contact. 



The factor of muzzling appears to have a more important influence, since 

 neither the muzzled goats nor their offspring developed goitre, whereas 50 per 

 cent, of the unmuzzled goats did. The prevention of the entry into the 

 alimentary tract of anything but clean food and water appeared to prevent 

 the entry of the infecting agent. This being so, the infecting agent must have 

 existed or generated in the plot of earth on which the animals were tethered 

 and which their own alvine discharges had grossly contaminated — a 

 conclusion which is supported by all reliable observations on man, animals, or 

 fish. My previous researches and those of Gaylord on salmonoid fishes have 

 shown that fish pollute the tanks, animals the soil, and man the dwellings 

 where they are confined in such a way as to give rise to goitre. Confinement 

 and ffecal pollution are the essential factors in its production ; without them 

 goitre does not arise. These conditions were fulBlled in the case of the 

 muzzled and unmuzzled goats alike, but in the former infection could not 

 occur, since muzzling closed its route. 



The factor of the presence of goitre in the mother is of great importance in 

 the genesis of congenital goitre in the offspring. Not only were 100 per cent, 

 of the offspring of the goitrous mothers in Class A born with congenital goitre, 

 but also congenital goitre occurred in two kids born of control mothers winch 

 had acquired goitre during their pregnancy. 



The influence of cultures administered also appears to be great. The 

 congenital goitres noted in Class A were, as a rule, of large size, while the 

 offspring was almost invariably stillborn, macerated, ill-developed and hairless, 

 an association of pathological characteristics which was not observed in the 

 controls of Class B, or Class C, and attributable, I think, solely to the greater 

 toxicity of the maternal blood in the animals of the former class. "Whether 

 this toxicity was due to the generation by the organisms contained in the 

 cultures of toxic substances after their implantation into the intestinal tracts 

 of the animals or to toxic substances contained in the original culture tubes 

 does not materially affect the argument, since in either event these substances 

 were the products of micro-organisms contained in the culture tubes and the 

 true causal agents of the malady. The toxic products of these organisms, 

 then, possess the property not only of inducing the development of large 

 goitres in the foetus but also of retarding foetal development and bringing about 

 its premature cessation. 



The conclusion sec forth in my former paper* is, therefore, confirmed. 



Congenital goitre is due to the action on the foetal thyroid of toxic 

 * ' Indian Journal of Medical Eesearch,' vol. 2, No. 1 (1914). 



