It is generally accepted that the intestinal manifestations of cholera are due to the action of endotoxin of Vibrio comma and that the question as to what extent this endotoxin is responsible for production of general signs and symptoms of the disease has remained a subject of much doubt (Pollitzer, Bull. World Health Organization, 13, 1075, 1955). Several workers have tried to reproduce the human disease in experimental animals, especially in the guinea pig, by feeding them cholera toxin (Bonis and Natale, Riforma med., 29, 141, 1913; Freter, J. Infectious Diseases, 97, 57, 1955) but without success. Some could demonstrate only the lethal action of the toxin whereas others could not even confirm it.

Dutta and Habbu (Brit. J. Pharmacol., 10, 153, 1955) developed a method of reproducing the disease in the infant rabbit. This method has been utilized for the study of cholera toxin. The toxin was prepared by the method of Gallut (Ann. inst. Pasteur, 86, 561, 1954) using the rabbit passaged strain of Inaba 569B, originally used by Dutta and Habbu. Each preparation of the toxin was tested for sterility and toxicity. Toxicity was evaluated in white mice weighing between 16 and 18 g. The LD50 of the toxin was found to be 0.25 ml and all the preparations were adjusted to this level of toxicity. After gastric lavage, rabbits 8 to 12 days old were starved for 12 hr. During this time they had free access to water. At the end of this period, the stomachwas washed again. The toxin was administered orally. The total calculated dose, which was5 ml for 100 g of body weight of the animal, was divided into four portions and each was given at intervals of 2 hr. For biochemical studies, heart blood was collected from those animals which showed signs of collapse. Simultaneously, control animals were studied. Sixteen of 20 infant rabbits fed toxin became sick within 6 hr. They became less active and huddled together. Diarrhea in the animals often