PROTECTIVE INOCULATIONS. 285 
The duration of the immunity resulting from these inoculations 
has not been definitely determined, although in a majority of those 
inoculated it appears to have afforded protection for at least five or 
six months. Haffkine’s method of preparing his material for protec- 
tive inoculations isas follows: A kilogramme of finely chopped goat’s 
flesh is macerated in diluted hydrochloric acid, and then placed in an 
autoclave and heated for six hours under a pressure of three atmos- 
pheres. ‘This is filtered, neutralized’ with KOH, and diluted up to 
three litres. The plague bacillus is grown in this medium. Accord- 
ing to Haffkine, when the bacillus is planted upon the surface of this 
medium, a characteristic growth results. If undisturbed for five or 
six days delicate thread-like processes are seen hanging in the culture 
medium resembling stalactites suspended from the roof of a cavern. 
This growth is said to be peculiar to the plague bacillus. To make 
the prophylactic the bacillus is grown in a darkened room in large 
flasks. In India it is unnecessary to use a thermostat. Five or six 
crops of the stalactites are grown and shaken to the bottom of the 
flasks. This takes about six weeks. The culture is then sterilized 
in a water bath at 70° C., the time required being about three hours. 
A little carbolic acid or thymol is then added, and the material, after 
shaking to distribute the bacteria, is decanted into small bottles. It 
is now ready for use, and is usually injected into the subcutaneous 
connective tissue in doses of two cubic centimetres. A second inocu- 
lation in from fourteen to twenty days is recommended by Leumann, 
and after this the blood of the inoculated individual usually gives the 
Widal reaction. a 
CHICKEN CHOLERA. 
Pasteur’s researches with reference to the etiology of the disease 
known in France as choléra des poules first led him to the discovery 
that a virulent culture of a pathogenic bacterium may become “ atten- 
uated” by certain agencies, and that immunity may be conferred upon 
susceptible animals by inoculating them with such attenuated culture. 
We now know that his microbe of fowl cholera is a widely distributed 
bacillus, which is frequently encountered in putrefying material, and 
that it is also extremely fatal to pigeons, pheasants, sparrows, rabbits, 
and mice. Also that the same or nearly allied species may produce 
an infectious disease of swine (Schwetineseuche), of cattle (Rinder- 
seuche), and of deer ( Wildseuche). 
Subcutaneous injection of a minute quantity of a virulent culture 
usually kills chickens within forty-eight hours. Some time before 
death the fowl falls into a somnolent condition, and, with drooping 
