420 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1939 



Out of 6,622 samples of diaphragm muscle tissue obtained from 

 1933 to 1937 from as many grain-fed hogs originating in Alabama, 

 Florida, Georgia, Illinois, Kentucky, Michigan, Minnesota, Missouri, 

 New Jersey, New York, and Ohio, and slaughtered in officially in- 

 spected establishments, only 60 (0.91 percent) were found to be in- 

 fested with trichinae. Of those found to be so infested, nearly one- 

 third contained between only 1 and 5 larvae per 100 grams of 

 diaphragm muscle tissue ; slightly over one-sixth of the positives con- 

 tained only between 6 and 25 larvae per 100 grams of diaphragm 

 muscle tissue; of the remainder, constituting 52 percent of the posi- 

 tive samples, one or more trichinae were found per gram of dia- 

 phragm muscle tissue, and only about two-thirds of these contained 

 in excess of more than one larva per gram of muscle tissue. 



Out of 6,484 samples obtained from as many hogs that had been 

 fed on uncooked garbage, 286 (4.41 percent) were found to be in- 

 fested. Of the samples so infested more than two-fifths contained 

 only from 1 to 6 larvae, and more than one-fifth contained only from 

 6 to 25 larvae per 100 grams of diaphragm muscle tissue; of the 

 remaining samples which contained one or more larvae per gram 

 of muscle tissue, only two-thirds contained more than one larva per 

 gram of such tissue.* Out of 1,987 samples obtained from as many 

 hogs known to have been fed cooked garbage, 11 (0.55 percent) were 

 found to be infested. Of those so infested, nearly 45 percent con- 

 tained only from 1 to 5 and about 18 percent contained only from 

 6 to 25 larvae per 100 grams of diaphragm muscle tissue. Of the 

 remaining 29 percent, which contained 1 or more larvae per gram of 

 diaphragm muscle tissue, only 0.9 percent contained more than 1 

 larva per gram of such tissue. 



These data show an incidence of trichinae in garbage-fed hogs 

 about five times as great as that in grain-fed hogs, and an incidence 

 of these parasites in hogs fed uncooked garbage about eight times as 

 great as that in hogs fed cooked garbage. The data show, therefore, 

 that the feeding of uncooked garbage favors the spread of trichinae 

 to swine and that the cooking of garbage is an effective method of 

 sharply curtailing the incidence of trichinae in garbage-fed hogs. 



* Since this paper was written a total number of 13,162 diaphragms from as many 

 ii:rain-fed hogs were digested with the following results : Only 126 (0.95 percent) were 

 found to contain trichinae and nearly two-thirds of the positives contained only 1 to 5 

 larvae per 100 grams of tissue ; less than 25 percent of the positives contained 1 or more 

 trichinae per gram of tissue. Out of 10,500 diaphragms from as many garbage-fed hogs 

 obtained from important garbage-feeding centers, 599 (5.7 percent) were found to be 

 infected. Of the positives 228 (38 percent of the whole) contained only 1 to 6 larvae per 

 100 grams of tissue ; slightly over 25 percent of these positives contained 1 or more 

 trichinae per gram of tissue. 



The available evidence shows that the majority of the positive grain-fed hogs had light 

 infections with trichinae, this being correlated with the preponderance of low-grade 

 human trichina infections brought to light by the examination of human diaphragms. 

 Grain-fed hogs constitute the vast bulk of swine in the United States. 



