LIVESTOCK PARASITOLOGY — SCHWARTZ 353 



food shall contain any muscle tissue of pork, unless that meat has been 

 refrigerated, or heated, or otherwise treated, in a manner that will in- 

 sure the destruction of trichinae. The background for these require- 

 ments lies in extensive investigational work carried out by Ransom 

 and his associates and by others in the Bureau of Animal Industry. 

 In 1913 Ransom determined, following exhaustive tests, that certain 

 low temperatures, compatible with the practical requirements of the 

 meat industry, destroyed the vitality of trichinae. Later investiga- 

 tions established the fact that the heating of pork to a temperature 

 of not less than 58° C, as well as certain curing procedures also de- 

 stroyed these nematode larvae. These findings, translated into action 

 by Federal meat inspection, have given to the American people for 

 several decades a protection from pork-containing products that 

 otherwise would have been the most fertile sources of trichinosis. 



EARLY INVESTIGATIONS OF INTERNAL PARASITES 



Aside from trichinae and a few other helminths of livestock, little 

 was known at the time the Bureau of Animal Industry was established 

 about the kinds of parasitic worms that occurred in our domestic ani- 

 mals, and even less was known about verminous diseases. Curtice, 

 Stiles, Ward, and a few others contributed much that helped to lay 

 a foundation upon which those who followed built a sizable structure 

 of knowledge of the helminths and the diseases they cause in food-pro- 

 ducing animals. In this address only the early work on the helminth 

 parasites of livestock will be mentioned. 



Even while sheep scabies was receiving preferred attention, it was 

 recognized that the internal parasites of ovines could not be ignored. 

 Stomach worms already had a reputation as being injurious parasites 

 of sheep, and it was assumed, moreover, that there might be others 

 that had the capacity of doing serious harm. It is not surprising, 

 therefore, that Curtice, who began his studies in the Bureau of Ani- 

 mal Industry in 1886, should have embarked on a study of the para- 

 sites of sheep. That study resulted in the publication of a treatise 

 on the subject, which contained much that was new and significant. 

 Perhaps the outstanding contribution made by Curtice, while engaged 

 in this study, was the discovery of the cause of nodular disease which, 

 because of the resemblance of its lesions to those produced by the 

 tubercle bacillus, had been considered as intestinal tuberculosis and 

 studied, therefore, from a bacteriological standpoint. Curtice de- 

 termined, however, that the nodules were caused by nematode larvae, 

 which he recognized to be the developmental stages of mature worms 

 localized in the large intestine, and named by him Oesopkagostomum 

 colunribianum. 



