CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 287 



would continue; but it seems doubtful if enough of such mature worms 

 would be consumed in this manner to cause any serious infectious. We 

 do not know, however, how long the worms are able to live outside of 

 the body in this developed condition ; if they can exist but a few days 

 the danger from them would be very slight, but if this period can be 

 prolonged for weeks or months the danger would be more serious, and 

 we might have at least a partial explanation of the many cases of in- 

 fection occurring where the condition of life among the hogs seems to 

 be all that could be desired. 



The young trichiuiTe or larva? which are produced in such enormous 

 numbers in the intestines within a few days after infected meat has been 

 eaten, and many of which are doubtless voided with the excrement, are 

 practically incapable of dangerously infectiug grounds or feeding places. 

 These cannot reproduce themselves until they have found their way 

 into the muscular system, and have been encysted for a time, so that 

 even a considerable number of such larvse taken into the stomach would 

 produce no appreciable effects. 



In the present condition of knowledge the tendency is to conclude 

 that by far the larger part of trichinous hogs are infected by eating the 

 flesh of some animal wbich has previously been infected in the same way. 

 Trichinae cannot develop or live for any considerable time in the bodies 

 of insects, cold-blooded animals, or birds, and, consequently, the infec- 

 tion must result from some of the warm-blooded animals, which either 

 habitually or occasionally eat flesh. Among these cats, rats, and mice 

 are the ones most frequently suspected; but an inquiry into the condi- 

 tions under which hogs are raised in the West has led us to doubt if 

 the infection could occur in any considerable number of cases in this 

 way. Hogs are usually kept in grass fields, where rats and mice are not 

 common, and where cats certainly do not abound, and in no part of the 

 hog-raising country is it a custom', so far as could be ascertained, to run 

 the hogs in corn-fields, where there would be an opportunity of their 

 finding rats and mice. 



It has been charged that there was a custom of feeding the hogs 

 which died from disease to the well animals, and that this accounted 

 for the trichinous infection. After an extensive investigation, however, 

 we feel authorized to state that this assertion is not correct. Such a 

 practice seems to have been followed to some extent a half dozen or 

 more years ago, but as the contagious character of hog cholera became 

 better understood, and as the demand increased for the cheap grease 

 rendered from such dead animals, they were more generally sold to 

 rendering establishments at a price considerably beyond what they 

 would be worth for animal food. The trichina? of to-day must therefore 

 be acquired from some other source than the hogs which die upon the 

 farms. 



The French and German authors have not hesitated to assume that 

 our hogs were infected by feeding upon offal from the slaughter-houses, 

 but this assumption could only have been made in complete ignorance 



