ABSTRACTS
321
minutes. Ordinary commercial vinegar was effective in 1: 100 strength after contract for five
to nine hours. Ordinary washing soda was found to be a most reliable agent. A 1 per cent.
solution destroys the virus within one hour, and a 4 per cent. solution at room temperature kills
the virus within 15 minutes. A 4 per cent. solution at 75° C. is effective within five minutes.
DETERMINATION OF IMMUNOLOGICAL TYPES OF VIRUS.
Strains Derived from British Outbreaks.—Twenty-three strains have been examined: 21
of them proved to be of the "O" type ; no "A" or " C" types were encountered. The two
remaining strains did not belong to any of the three recognised types and they also differed from
each other. Altogether 40 British strains have now been examined and 37 have proved to be of
the "O" type.
FOOT-AND-MOUTH DISEASE IN THE RAT, IN THE MOUSE, AND IN THE HAMSTER.
Two cases are reported in which tissues from common rats have caused infection when inocu-
lated into guinea pigs. One of these rats was caught on a farm which was under control on
account of an outbreak of foot-and-mouth disease, and the second was caught on the Experimental
Station, Pirbright. A feature of the spontaneous disease in rats has been the absence of typical
lesions, but inoculation of tissues from affected rats into guinea pigs produces the disease. Thirty-
three rats were infected by placing them in contract with inoculated reacting rats. Successful
attempts were made to transmit the infection from rat to rat by ingestion of rat carcasses. Four
guinea pigs reacting to rat strain virus were killed and the carcasses, minus feet, were thrown to
three pigs which showed typical foot-and-mouth disease vesicles within four days. White rats were
readily infected by inoculation and by ingestion of infected carcasses, but infection by contact
was less successful than with the wild rats.
Excellent plates of drawings and paintings in colour and some photographs, show the types of
lesions found in this experimental work on the rat.
House mice were not infected, but, after some failures, white mice reacted with poor lesions.
The hamster was shown to be susceptible to inoculation, primary lesions being followed by gene-
ralisation.
FOOT-AND-MOUTH DISEASE IN CATTLE AND PIGS.
Natural Resistance.—Excluding definitely a typical strains of virus, it has been found that
1.7 per cent. of cattle and 5.3 per cent. of pigs resist infection by intramuscular inoculation.
Occurrence of the Virus in the Blood, Urine, and Milk.—The presence of the virus in the
blood during the period of incubation has not been demonstrated until shortly before the beginning
of the reaction. Virus may appear in the blood in considerable concentration some hours before
the rise in temperature or the appearance of vesicles Virus appears in the urine quite irregularly
and it may make a transitory appearance during the incubation period or even as long as 46
hours before the rise in temperature or the appearance of vesicles. The milk from one cow was
shown to contain virus four hours before the temperature reaction had gained the peak of the
curve.
The Time of Appearance of Natural Infectivity.—As a rule animals do not appear to be
infective during the incubative stage of the disease. Where the temperature rose before any
vesicles developed, no evidence was found that the thermal reaction is associated with infectivity
for other animals. It would appear that no animal was infective until it showed definite vesicles.