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 is as 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 grow r n 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 beiug 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 Leumaun, 

 and after this the blood of the inoculated individual usually gives the 

 Widal reaction. 



CHICKEN CHOLERA. 



Pasteur's researches with reference to the etiology of the disease 

 known in France as cholera des ponies 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 (Schweineseuche), of cattle (Hinder- 

 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 



