498 THE CHOLERA VIBRIO 



of the nucleo-protein dissolved in 1 c.c. of slightly alkaline water are inoculated 

 sub-cutaneously. 



Strong's vaccine for human inoculation is prepared by making an emulsion 

 in sterile water of vibrios from an agar culture, sterilizing at 60 C., macerating 

 at 37 C. for 2 days, and filtering through a Reichel bougie. In large doses 

 the product is fatal to rabbits but in smaller doses acts as a vaccine. If 

 inoculated in doses of 3-4 c.c. in man it produces a slight reaction and the 

 serum of the inoculated person is afterwards bactericidal and agglutinating. 



V. Besredka's vaccine. Besredka succeeded in conferring rapidly a lasting 

 immunity on rabbits without setting up an inflammatory reaction by inocu- 

 lating them sub-cutaneously with a vaccine prepared by sensitizing the bodies 

 of the vibrios with an anti-choleraic serum (see typhoid bacillus and plague 

 bacillus). 



VI. Vaccination against choleraic peritonitis. Guinea-pigs are very easily 

 immunized against peritoneal infection. Intra-peritoneal inoculation of 

 vibrios killed by heat is efficient in preventing a subsequent choleraic peri- 

 tonitis. To obtain a lasting immunity the single inoculation of dead vibrios 

 should be supplemented by several inoculations of living organisms. 



Klein has shown that the products of organisms other than the cholera vibrio can 

 induce immunity to choleraic peritonitis : intra-peritoneal inoculation of small 

 doses of a heated culture of the Micrococcus prodigiosus will immunize guinea-pigs 

 against fatal doses of the vibrio. Israel has found that sterile broth inoculated 

 intra-peritoneally will also immunize guinea-pigs against choleraic peritonitis. 

 Inoculations of human serum (vide infra), of normal saline solution or of urine all 

 act in a similar manner (Israel, Metchnikoff). The explanation of these phenomena 

 is to be found in the fact that the substances inoculated stimulate phagocytosis, with 

 the result that the leucocytes ingest the vibrios and so arrest the peritoneal infection. 



VII. Vaccination with toxin. Metchnikoff, Roux and Taurelli-Salimbeni 

 showed that animals very quickly become accustomed to cholera toxin and 

 that guinea-pigs, rabbits, horses and goats may be immunized by inoculating 

 them with toxin. 



When guinea-pigs and rabbits are treated with small doses of toxin the temperature 

 rises for a short period after each inoculation and then falls below normal for about 

 20 hours. Repeated inoculations are accompanied by a certain loss of weight from 

 which the animals soon recover, though rabbits are slower in picking up than guinea- 

 pigs : the inoculations should be withheld until the animals have regained their 

 original weights. It is somewhat difficult to immunize rabbits satisfactorily. 



The inoculation of 2-4 c.c. into goats is followed by a rise of temperature which 

 becomes less marked as the animal becomes accustomed to the inoculations. 



Horses react sharply to sub-cutaneous inoculation of the toxin and show a well- 

 marked and persistent oedema at the site of inoculation. For purposes of immuniza- 

 tion it is better to adopt the intra-venous method, commencing with very small 

 doses (always dilute the toxin with an equal volume of normal saline solution on 

 account of the high degree of alkalinity of the former). Inoculation into the veins 

 is followed by a more or less marked reaction (fever, diarrhoea, etc.) ; an interval 

 of about 10 days sufficient to allow the animal to recover completely from the pre- 

 vious dose should elapse between each two inoculations. After about 6 months, 

 50-60 c.c. can be given at a single inoculation. The horse is bled 12 days after the 

 last inoculation. 



5. Serum therapy. 



The serum of animals vaccinated against the cholera vibrio exhibits pro- 

 phylactic properties (Klemperer). 



Lazarus has shown that the serum of persons who have recovered from an 

 attack of cholera also possesses considerable prophylactic properties : in 

 some cases 1 c.c. of serum will protect a guinea-pig against choleraic peri- 

 tonitis. The prophylactic property of the blood however plays no part in 



