84 EXPERIMENT STATION EECORD. [Vol.36 



lyembrane of the larynx should also be considered along with the other lesions 

 mentioned. 



" Hemorrhagic laryngitis has been found in about three-fourths of a series of 

 500 pigs, killed subsequent to inoculation with hog-cholera virus, these hemor- 

 rhagic lesions being in evidence most regularly in those animals killed and 

 autopsied eight to eleven days after inoculation. In view of the fact that 

 petechial hemorrhages in the kidneys occur in a number of diflferent patho- 

 logical conditions, veterinarians should be cautious about basing a diagnosis on 

 this lesion alone, even though this lesion does appear in a very large percentage 

 of cases of hog cholera due to the filterable virus." 



Observations on 2,800 pigs inoculated with hog-cholera virus, H. P. 

 HosKiNs {Jour. Amer. Yet. Med. Assoc, 49 {1916), No. 6, pp. 817-829, fig. 1).— 

 Observations and experiments on 2,S00 pigs inoculated for the production of 

 hog-cholera virus at the Minnesota state serum plant over a period of approxi- 

 mately two years are reported. 



Of the pigs inoculated 390 (13.9 per cent) failed to succumb to the infection, 

 and their reactions varied between wide limits, indicating all grades of sus- 

 ceptibility and immunity to hog cholera. No pig survived a temperature higher 

 than 107.4° F. Only 8 per cent of the pigs weighing between 40 and 50 lbs. 

 survived the inoculation, thus indicating the greatest .susceptibility at this 

 weight. Pigs weighing between 50 and 60 lbs. at the time of inoculation showed 

 the greatest resistance. The resistance was found to slowly decrease, however, 

 as the pigs became heavier. Pigs which failed to succumb reached the height 

 of their reaction most frequently on the sixth day. Animals which died or 

 were killed when moribund reached the height of their reaction most frequently 

 on the seventh day. 



A virus was obtained (" fixed virus ") which could be depended upon to bring 

 pigs down on the eighth day with a fair degree of regularity by frequent 

 passages of a strain of virus through susceptible pigs an<l by carefully selecting 

 the seed virus pig from each group. Pigs inoculated with virus of different 

 ages up to 1G2 days succumbed quite reguhirly within a few days of the time 

 necessary for the same virus to bring the pigs down when comparatively fresh. 

 Virus 216 days old had lost its infectivity. Pigs inoculated with various 

 amounts of the virus (1 to 10 cc.) came down in the regular time, regardless 

 of the exact amount injected or the manner of introduction. 



Failure to succumb is considered by the author to mean that the pigs either 

 did not die of the disease or did not at any time become sick enough to warrant 

 slaughter for the purpose of obtaining virus. 



The attenuation of hog-cholera virus, D. J. Heai.y and E. J. Gott {Jour. 

 Infect. Diseases, 19 {1916), No. 4. pp. 569-571).— The authors at the Kentucky 

 Experiment Station, continuing the work on the etiology of hog cholera, report 

 experiments in which the virus of the disease was so modified by incubation 

 for 48 hours at 37° C. with hyperimmune blood that when injected it no longer 

 rendered normal hogs sick but even protected them when they were later ex- 

 posed to infection. The cholera virus incubated with normal rabbit serum for 

 48 hours at 37° was modified to the extent that one of three animals was pro- 

 tected against the disease. 



It is indicated that " it is quite possible that the mixture of hog-cholera virus 

 and hyperimmune blood which had been modified by incubation for 48 hours^ 

 at 37° and then rapidly dried over sulphuric acid at a low temperature woult 

 Indefinitely retain Its power to protect hogs against cholera, and yet not sicken 

 them." 



