CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 425 



oannot be too strongly insisted ou. Eats are probably the main source 

 of ti'icliinia spiralis in pi^s, as the infected rat, with its muscles wasting 

 as tlie result of the lodgment in their fibers of myriads of the encysted 

 trichinia, becomes correspondingly weak and inactive, and is easily 

 caught and devoured by the omniverous animal. If, then, we take the 

 observation of Dr. Bellfield and Mr. Attwood as a basis, and accept as 

 a fact that S per cent, of the hogs killed in Chicago are trichinous ; add 

 to this that the discovery of these worms in American hams and bacon 

 has led to the closure of several European markets against these prod- 

 ucts ; and, finally, that this specific fever of swine may be contracted and 

 conveyed by rats, and we have cause enough for the closer supervision 

 of the breeding of swine, and for a systematic desti^uction of rats wher- 

 ever either trichiuiasis or the sviiue plague has manifested itself. The 

 swine breeders themselves should be warned against this source of dis- 

 ease and loss, but the sanitary authorities should follow up every case 

 of trichinia sis and hog cholera, and see that the rats are not allowed to 

 become active in its jiropagatiou. 



INFECTION BY INOCULATION OF CULTIVATED VIRUS. 



My last experiment was made with a material which might have been 

 supijosed to have been thoroughly disinfected. A little pleuritic fluid 

 swarming with actively moving bacteria was added to some milk and 

 boiled for five minutes. "W hen cold, a drop or two of ammonia was added, 

 the neck of the glass vessel plugged with cotton wool, and the whole 

 j)laced in an incubator at 98° F. for two days. A second and third por- 

 tion of boiled milk and ammonia were successively inoculated from the 

 first and second, and a little of the milk with the third generation 

 of the cultivated poison was injected under the skin of a healthy pig. 



The subject suffered from illness with red and purple spots on the 

 skin and a greasy black exudation ; was killed on the twenty-first day and 

 immediately dissected. The stomach was extensively discolored, of a dark 

 brownish red, becoming a bright red at the margins. The small intes- 

 tines were congested and showed punctiform pectichiae, especially on the 

 duodenum and on the ilieum near the ileo-caecal valve. The large in- 

 testine had enlarged follicles and patches of congestion, and the lym- 

 phatic glands of the bowels were discolored a deep red. Elsewhere the 

 lymphatic glands were either reddened or pigmented. The lungs and 

 liver showed little change, but there were purple discoloratious on the 

 kidneys and heart. 



This case was evidently one of the specific hog fever, and, unless some 

 source of fallacy entered, seems to imply that the germs of the disease 

 may on certain conditions resist for a time the heat of boiling water. A 

 single experiment is, however, too narrow a basis for the support of a 

 theory, and I shall therefore content myself with merely recording the 

 result, and leave the matter to be made the subject of a more crucial 

 test at some time in the future. 



Perhaps the most remarkable feature of these experimental inocula- 

 tions is the fact that the pigs inoculated from the infected sheep and 

 rats appeared to take the disease in a mild form, and in all such cases it 

 seemed probable that, had the animals not been sacrificed by the knife, 

 a recovery might have ensued. In the case of the pigs inoculated from 

 the sheep, one (^o. -1) was twioe inoculated, thii-ty-eight and twenty- 

 three days before it was killed, and although the disease showed itself 

 in an unequivocal form, yet it was not severe and did not promise a fatal 

 result. A second (Xo. 7), inoculated from the lamb twenty-one days be- 



