Ey) 
VESICULAR STOMATITIS OF HORSES AND CATTLE i 
outbreak, which lasted about a month, 33 herds, containing in all 
approximately 700 animals, became infected. Inoculation » experl- 
ments on such laboratory animals as rabbits, rats, and mice have 
resulted negatively, but guinea pigs can be regularly infected by 
inoculation through scarification on the metatarsal pads, and less so 
by intra- abdominal injection. Attempts, however, to infect them by 
natural exposure have not been successful. The disease manifests 
itself in susceptible animals more rapidly after the application of 
infectious material to scarified areas in the mouth than through 
intravenous injection, although positive results have been obtained 
also by the- latter method. Incculations made on the upper suriace 
of the tongue are more likely to take than if made elsewhere. The 
freshest material that it is possible to obtain should be used in 
making the inoculations. 
Contrary to experiences in the field, the bureau was able in several 
test inoculations to transmit infection to the feet of cattle in a small 
proportions of cases, and likewise also produced lesions in from 5 
to 9 days in the feet of one hog, in the mouth of another, and on 
the snout of the third. While these cases were the exception and 
not the rule, they should be recorded for their scientific interest. In 
this connection it should be stated also that a number of hogs in 
immediate contact with these animals but without receiving any arti- 
ficial inoculation remained normal in all cases, while a number of 
cattle similarly exposed contracted lesions which were confined solely 
to the mouth. 
IMMUNITY 
An attack of the disease caused by one of the two known viruses 
has been shown to protect one lot of guinea pigs against an inocula- 
tion with the same strain of virus for at least a year, and another lot 
2 years, but does not afford protection against the other virus. A 
number of horses and cattle which were typically affected at the 
bureau experiment station failed to contract the disease when inoc- 
ulated with the virus 3 months later, although the control animals 
became infected promptly. In these cases immunity lad persisted 
for at least 3 months. Further tests regarding its duration could 
not be made ai the time because the required infectious material was 
not obtainable, since the disease had disappeared. More recently 
three cows that had recovered from an attack of the malady failed 
to develop it again 5, 7, and 714 months, respectively, later, ;vhen 
inoculated with virus proved to be virulent. Still more recently 
(19380) two cows that had had the disease 4 years and 7 months 
previously resisted an exposure through inoculation which nes the 
disease to develop in two susceptible cows and two guinea pigs inoc- 
ulated with the same material. 
The results of these tests, though made on a limited number of 
iarge animals, coupled with the fact that guinea pigs remain immune 
for a long time following an attack of the disease, indicate that im- 
munity in cattle, and also likely in horses, is fairly lasting. 
Whether the milk of affected cattle is or is not infectious for 
people has not been recorded, but such milk has been fed experi- 
mentally to hogs without producing any ull effects. 
