Microhic Diseases Indwidually Considered. 215 



of the bacillus of pneumo-enteritis have been made by 

 MM. Cornil and Chantemesse. They had recourse to the 

 action of heat upon cultures. A culture maintained 

 at 43° during seventy-four days produces only a local 

 abscess in the rabbit but is still regularly toxic for' the 

 guinea pig. After ninety days the virus no more 

 kills guinea pigs ; they contract an abscess at the 

 point of inoculation, whilst rabbits often escape even 

 this lesion. The virus thus attenuated transmits its 

 special virulence to its descendants and confers, on 

 guinea pigs and rabbits which have received it, im- 

 munity for virus which has been heated only seventy- 

 four days ; the latter acts in the same way toward 

 more active and the natural virus. It is therefore 

 possible to vaccinate the rabbit and the guinea pig 

 against pneumo-enteritis. Unfortunately this method 

 of prevention, applied to the pig, has not given the 

 same result, and a process of vaccination is yet to be 

 found for this species. 



The vaccine of rouget does not vaccinate hogs 

 against cholera, a circumstance which increases the 

 importance of the differential diagnosis. 



Schweinitz has succeeded in vaccinating- the sruinea 

 pig by means of soluble substances which he has iso- 

 lated from cultures.* 



* [Billings obtained protection against this disease by inocula- 

 tion of pigs with cultures derived from mild cases of the natural 

 disease. A certain proportion of the animals die from the inocu- 

 lation. Neh. Ag. Exper. Sta., Vol. 2, No. 4. Selander (confirmed 

 by Metschnikoff) found that cultures of the Danish swine-pest, 

 increased in virulence by passage through pigeons, produced in 

 the blood of rabbits very active toxines. When such blood was 

 sterilized at 57° C. and injected in rabbits it conferred a solid im- 

 munity. The serum of rabbits thus vaccinated was also iouud to 



