i8o6 



THE CHOLERAS 



route of its march. The reason of this is not clear. Certainly 

 climatic conditions may be of importance, and perhaps a low level 

 of the subsoil water and a high earth temperature, together with an 

 imperfect sewage disposal and contaminated source of the drinking- 

 water of the place, may have something to do with this anomaly. 



Another point which is by no means understood is the fact that 

 the disease remains for years in the endemic region, and then 

 suddenly spreads in epidemic and pandemic form, extending at 

 times over the whole world. 



The aetiology may, therefore, be summarized by saying that the 

 disease is caused by Koch's Vibrio cholerce acting in the presence 

 of some unknown bodily condition or conditions, and spread directly 

 from man to man by fomites, water, insects, and food, but the 

 reasons for its endemicity and epidemicity are unknown. 



When travelling from one place to another, it always adopts 

 channels of human intercommunication, which may be ships, rivers, 

 roads, or railways. When introduced into a locahty, it will give 

 rise to a widespread epidemic if the sanitation is so defective that 

 the germs gain access to the drinking-water, but will be far less 

 extensively spread if due to food or insects, and will be merely 

 sporadic if spread from man to man. 



Pathology. — ^The vibrio grows in the lumen, the glands, the 

 epithelial cells, and the mucosa of the small intestine, probably 

 producing an endocellular toxin, which is set free and causes the 

 symptoms. 



The question of toxin formation has, however, been much debated. 

 Thus, in 1905, Brau and Denier considered that they had obtained 

 a soluble toxin. In 1906 Kraus said that he had obtained a soluble 

 toxin which caused the disease, and in the same year MacFadyen 

 obtained a virulent endotoxin. In 1907 Strong carefully investi- 

 gated the subject, and concluded that he was unable to find a 

 soluble toxin as described above, but that MacFadyen's endotoxin 

 was the true toxin which caused the symptoms in man. This endo- 

 toxin causes great gastro-intestinal disturbance, leading to the 

 passage of fluid from the blood to the bowel in the following order: 

 First water, and then inorganic salts, especially sodium chloride; 

 later, phosphates and potassium salts; and still later organic sub- 

 stances. This endosmosis causes a great concentration of the blood, 

 producing a high specific gravity, which may reach 1073 to 1078, 

 which is associated with a great increase in the erythrocytes- — 

 8,000,000 per cubic millimetre, according to Rogers and Megaw — 

 with a corresponding increase of the haemoglobin and of the leuco- 

 cytes, which may number from 14,000 to 60,000 per cubic miUimetre. 

 At the same time the alkalinity of the blood is decreased and its 

 coagulative power altered, while the oxygen contained therein is 

 decreased. 



The decrease of the alkalinity of the blood may be very marked 

 in severe cases, and Rogers, Sellards and Shaklu give great import- 

 ance to this so-called cholera acidosis. 



