DU CHARBON BACTERIEN. 
501 
Preventive Inoculation. 
Immunity can be conferred by inoculating natural virus— 
A. —In the connective tissue, if but a minimum quantity of 
microbes enter. 
B. —In the connective tissue of the tail, where but little ab¬ 
sorption takes place, but tin's method is also uncertain in its results. 
C. —In the veins ; 3-10 of a drop of fresh virus for a sheep, 
and 3, 5 to 10 drops for cattle. 
To obtain the virus, inoculate a guinea-pig; take 2 parts of 
muscle from the black tumor and one part of water; filter first 
through linen and then through 2 or 3 layers of fine batiste; mix 
liquid thus prepared with 5 times its quantity of water. The 
jugular is carefully exposed by dissection and the injection made 
so as to avoid touching the walls of the vessel with the virus. 
A detailed account of the mode of performing the operation 
is given, and should be consulted before attempting a series of 
operations. 
D. —Injection in the respiratory tract can be made experi¬ 
mentally, but it is not of practical application. 
Immunity Conferred by Attenuated Virus. 
The virus can be attenuated— 
1st.— By the action of antiseptic substances , but the effect is 
uncertain, and is as yet merely a laboratory fact. 
2d.— By successive cultures. The virulence is often dimin¬ 
ished after the fourth or fifth culture, but the amount can only 
be determined by experiments. 
3d.— By the action of heat on fresh virus. A temperature of 
65° C., prolonged for 15, 20, 30, 40 and TO minutes, gives a 
virus of decreasing strength. Slight variations will, however, so 
alter the results that the attenuations cannot be depended upon. 
4th.— By action of heat on dried virus. After diluting the 
dried virus (1 part) in water (2 parts), the preparation is placed 
in a stove and heated for seven hours.* 
* The experience of the au'hors has shown that no appreciable effect is ob¬ 
tained below 65° C. 85° C. makes an attenuated virus which serves well for a 
second inoculation, but is still too strong to be safe with the smaller animals, or 
with very susceptible cattle. 100° C. produces an excellent first inoculation, and 
can be used safely even with guinea pigs. The first and second inoculations are 
made eight days apart. 
