a 
1 May, 1900.} QUEENSLAND AGRICULTURAL JOURNAL. 423 
Animal Pathology. 
BLACKLEG OR QUARTER-ILL. 
ABsrracts From A Reporr py VICTOR A. NORGAARD, V.S., 
CoPpENHAGEN, 
Chief of the Pathological Division, Bureau of Animal Industry, U.S.A. 
_ Preventive Vaccination —Vo Arloing, Cornevin, and Thomas belong the 
honour of first discovering that animals may be protected against blackleg by 
jtoculation with more or less virulent material obtained from animals which 
ave died from blackleg. They found that the hypodermic injection of 
Minimal doses of fluid froma blackleg tumour did not necessarily result in 
death, but frequently produced a mild attack of the disease, unaccompanied by 
‘ny swelling, and that animals treated in that way were afterwards possessed of 
“very high degree of resistance against the disease. ‘lhere are, however, few 
lseases where the individual susceptibility varies to a greater extent than is the 
se in blackleg, and, as it was impossible to ascertain beforehand the degree of 
‘usceptibility or power of resistance possessed by each animal, the exact dose 
employ in each case could not be determined, and the method was abandoned 
‘8 being too dangerous. Even when the inoculation was made at the extremity 
of the tail it frequently resulted in the development of a swelling which spread 
| © the rump and killed the animal, or else the tail became gangrenous and 
| cropped off. 
| When the virus, either fresh from a tumour or dried, is introduced into 
the blood-stream or into the trachea. the animal shows great resistance to its 
Sttect, and subsequently becomes immunised. It is, however, rather difficult to 
iMect the virus either into the jugular vein or into the trachea without infecting 
te surrounding connective tissue, and the technique of the operation is too 
‘omplicated to be of practical value when large numbers of cattle are to be 
Yaccinated. Nevertheless, the French scientists practised it on 500 animals 
_ “ith one death only resulting from the operation. 
Attenuated Virus.—Prolonged exposure to a high temperature serves to 
‘tenuate the virulence of either fresh or dried virus. ‘Nhe fact was employed 
Y the above-mentioned authors for the preparation of a vaccine which may be 
‘wed in everyday practice with little danger of injuring the cattle. The material 
“sed for the vaccine is obtained from a fresh blackleg tumour, by pounding the 
Nuscle tissue in a mortar with the addition of a little water, and squeezing the 
Pulp through a piece of linen cloth. The juice is spread in layers on plates 
‘nd dried quickly at a temperature of about 85 degrees C. This temperature 
_,0es not in the least affect the germs, and the dry virus obtained in this way 
| tetains a high degree of virulence for a couple of years or more. 
When vaccine is to be prepared, the dried material is pulverised and mixed 
| Ma mortar with two parts water until it forms a semifluid homogeneous mass. 
This is spread in a thin layer on a saucer or glass dish, and placed in an oven, 
. the temperature of which may be regulated with exactness. The reason for 
itixing the virus with water is to insure a quicker and more uniform attenua- 
°n, ‘The temperature of the oven is previously brought up to 100 degrees to 
' +04 degrees C., and the virus is allowed to remain in it for seven hours. When 
"emoved, it appears as a brownish scale, which is easily detached from the dish. 
Y is scale is pulverised and mixed with water, and when inoculated under the 
‘tin of calves in doses of 1 centigram per head it produces partial immunity. 
Ubsequent inoculation with virus which has been heated for the same length 
°f time, but, at a temperature of 90 degrees to 94 degrees C., serves to re-enforce 
€immunity. The inoculation is followed by insignificant symptoms. Ina 
