NOTES ON ATTENUATION OF VIRUS TO PREPARE A VACCINE. 
331 
but without such records before us it has been generally under¬ 
stood that the preparation of a true hog cholera vaccine from the 
virus held in cholera blood, by applying heat, was impracticable. 
The great demand in Kentucky for Dorset-Niles anti-hog cholera 
serum prompted a few experiments along this line, in that if a 
successful vaccine could be prepared, we could come that much 
nearer supplying the demand for immune hogs in our state. 
The manufacture of the Dorset-Niles anti-hog cholera serum 
was not discontinued for these experiments, nor were such ex¬ 
periments carried on in the field, but they were conducted at the 
laboratory in conjunction with serum production. The two 
works at times were conflicting, but the few collected experi¬ 
ments on about sixty hogs inoculated with attenuated virus may 
serve to confirm the unreliability of this procedure or excite 
criticism by those who have been more successful in producing 
immunity against hog cholera in swine by this method. 
* Drs. Dorset and Niles have recently conducted an experi¬ 
ment including the inoculation of twelve hogs with virus con¬ 
tained in cholera blood, after attenuating one-half hour, at 60 
degrees C., which resulted in the death of eleven hogs from acute 
cholera, the other developing the chronic form of the disease. 
** Dr. A. T. Peters, of Illinois, records success by this 
method; in fact, inoculation experiments include 16,000 hogs, the 
results of which had not all been received. His work extends 
into the field as shown by the large number inoculated, at the 
owners’ request, after being advised of the uncertainty of results. 
His method of attenuating virus consists of drawing off the clear 
serum from the cholera blood and attenuating at 6o° C., for one- 
half hour. The attenuated product is then carbolized and used 
in the following dosage: 
50-pound pigs, 2 cubic centimetres; 
ioo-pound pigs, 2V2 cubic centimetres; 
200-pound pigs, 3 cubic centimetres, 
and 1 cubic centimetre for each additional 100 pounds. 
* Report of Dr. M. Dorset, U. S. Live Stock Sanitary Proceedings, 1911. 
** Repcrt of Dr. A. T. Peters, U. S. Live Stock Proceedings, 1911. 
