TRICHINOSIS— SCHWARTZ 425 



tion with the 120,000 larvae each, showed up to 2,700 larvae per gram 

 of diaphragm muscle tissue, while pig 26, weighing 90 pounds at the 

 time of infection with 174,000 larvae, contained only 2,100 larvae per 

 gram of diaphragm muscle tissue. That many larvae may go astray 

 in the course of their migration through the body has already been 

 mentioned in the account of the life cycle of Trichinella spiralis. It 

 is probable that other factors, including the host's defense mechanism, 

 may be involved in the degree of the resulting infection. 



In the hope of securing more precise information on the symptoms 

 of experimental trichinosis in swine than was afforded by the data 

 already presented, the writer, in collaboration with Underwood and 

 Cross, infected seven pigs with varying doses of trichina larvae. 

 These host animals were under careful observation at the Agricultural 

 Research Center, Beltsville, Md., tliroughout the period during which 

 the severe symptoms would be expected to manifest themselves, and 

 for some time after this period. During the period of observation, 

 the pigs were carefully scrutinized, temperature, pulse, and respiration 

 rates being taken at frequent intervals and a general physical 

 inspection being made at each observation. 



Four pigs weighing 20.45, 20.91, 22.27, and 22.27 kilograms (45, 46, 

 49, and 49 pounds), respectively, were fed trichinous meat, the. num- 

 ber of larvae administered to the individual pigs being 10,000, 15,000, 

 20,000, and 25,000, respectively. The four pigs were under careful 

 observation for 50 days, 2 days prior to and 48 days following the 

 feeding of the infected meat. During this period the animals were 

 examined on 37 different days, without showing the slightest devia- 

 tion from the normal. On postmortem examination, 50 days after 

 infection, no macroscopic lesions of any kind were found. The 

 trichina content of these pigs per gram of muscle tissue was estimated 

 by obtaining and digesting 200 grams of muscle tissue taken from 

 different portions of the body, including the diaphragm. The num- 

 ber of trichinae per gram of mixed muscle tissue was 52, 46, 77, and 

 149, respectively. The weights of these host animals, determined 

 shortly before they were killed, were 37.25, 30.91, 35.91, and 36.82 

 kilograms (72, 68, 79, and 81 pounds), respectively. Considering the 

 ration fed, the increase in weight was nearly normal. 



Three other pigs, weighing 22.73, 22.5, and 19.32 kilograms (50, 

 491/2, and 42i/^ pounds), respectively, were infected Avith larger doses 

 of larvae, the doses being 50,000, 75,000, and 100,000 larvae, respec- 

 tively. These pigs were kept under observation for 83 days, during 

 which they were carefully scrutinized 3 times before and 19 times 

 after infection. The examinations of these host animals were made 

 about 4 to 5 days apart in most instances, except during the second 

 and third weeks of infection, when more frequent observations were 



