1889.] PUBLIC DOCUMENT — No. 34. 131 



who habituiilly send their hogs to the large private slaugh- 

 tering houses of the city, and who do not receive the viscera 

 from those institutions. Such is the practice of most of the 

 large raisers in the vicinity of Boston, and in particular is 

 true of all of the 50 raisers enumerated in Table III.* 



The only other suspected source, aside from the rats, is the 

 ordinary food of the hogs. In all cases, without doubt, this 

 is to some extent kitchen offal. In the case of 51 out of the 

 56 raisers enumerated in Table III., city offal is known to 

 constitute a large share of the food given to the hogs. 



It may prove to be merely a coincidence, and of no im- 

 portance, that hogs which are fed on city swill show a 

 proportion of trichinous individuals far in excess of those 

 which come from the West, among which offal-fed animals 

 must be much less numerous than here ; but it is a coinci- 

 dence which at least merits a careful examination. 



The probable sources of the principal part of the infection 

 in this vicinity appear to me to be limited to these two, — 

 rats and city offaL The only way to ascertain which of the 

 two is the greater source of danger, is to eliminate as far as 

 possible one of the supposed causes, without interfering with 

 the previously existing conditions of the other. It will 

 evidently be easier to control the nature of the regular food 

 of hogs, than to eliminate the rats. With honest super- 

 vision, there need be no doul)t of the completeness of 

 the experiment in excluding all uncooked meat ; but, with 

 the most scrupulous attention, it might not be possible to 

 secure absolute exclusion of rats, and the uncertainty in this 

 respect would render the experiment less satisfactory than 

 the control of the regular food. 



There are also certain facts which seem to me already to 

 point to the offal as the more probable source of the diffi- 

 culty. That being the case, there would be greater hope of 

 ascertaining the principal cause quickly, if this source were 

 the first to be removed. One of the facts which seems to me 

 to point to the offal rather than to the rats, is that so large a 

 proportion of all the hogs are thus infected. It seems 

 improbal)lc that every eighth hog should tind the opportunity 



* It is a common thing, however, for some of these raisers themselves to slaughter 

 a portion of their hogs for the purpose of supplying neighboring retail dealers. 



