Pathogenicity. 147 



Pathogenicity. Colon bacilli originating from tlie bodies 

 of calves which die from white scours exert a severe pathogenic 

 action on newly born calves. If a one-day-old calf is given 5 

 to 6 cc. or even only i^ to % cc. of the bouillon culture mixed 

 with milk, fever and diarrhea set in the following day and 

 the animal dies in frorn li^ to 3 days. The autopsy reveals a 

 hemorrhagic inflammation of the abomasum, and to a slight 

 extent also of the intestines. The contents of the intestines are 

 fetid and the mesenteric lymph glands show hemorrhagic swell- 

 ing. The injection of 5 cc. of bouillon culture into the rectum 

 of a new born calf has similar results, and sometimes the sub- 

 cutaneous injection of such a quantity of culture is fatal, while 

 1 cc. of culture has no ill effects upon the animal (Jensen). 

 A fatal infection per os may be much more easily produced 

 in calves in which the organs have not yet performed their 

 functions than in those in which the stomach and intestines 

 have already been set in activity by the ingestion of food 

 (Joest). Injection of culture into the umbilical vessels, in the 

 amniotic sac or into a vein produces in some cases a fatal 

 septicemia (Poels, Joest). Intraperitoneal inoculation of rab- 

 bits and guinea pigs causes a fibrinous peritonitis (Jensen, 

 Willerding), and sometimes subcutaneous injections of large 

 quantities of culture are also fatal to these animals as well as 

 to mice (Mazzanti & Vigezzi, Joest). 



The colon bacilli which are found in calves affected with diarrhea 

 correspond in all their morphological characteristics with the colon 

 bacilli isolated from the excrements of healthy calves. They differ, 

 however, from them by their severe pathogenic action on calves. Ac- 

 cording to Jensen the pathogenic colon bacilli are facultative parasites 

 which enter the digestive tract soon after birth, either with the first 

 milk or with other material swallowed by the animals (for instance 

 with mucus contaminated with sjraw). Under normal condition the 

 bacteria multiply in the intestinal canal only to a moderate extent, 

 and are harmless, as they are not capable of attacking the mucous 

 membrane of the healthy intestines. If, however, the resistance of 

 the tissues is weakened from some cause (cold, poor nutrition, etc.), 

 the bacteria penetrate into the intestinal wall and later also into the 

 distant organs as well as into the circulation and produce in this 

 manner an affection of the animal. 



The great susceptibility of calves which have not yet taken any 

 food may be explained by the fact that the colon bacilli which enter 

 the stomach before the ingestion of the colostral milk pass without 

 interference into the small intestines as the stomach has not yet pro- 

 duced any gastric juice. Owing to the absence of the intestinal juices 

 the meconium which is present in the intestines affords a favorable 

 medium for the multiplication of bacteria. Their penetration into the 

 mucous membrane is probably also facilitated by the fact that the 

 intestinal epithelium does not at that period possess a mucous covering, 

 and is therefore easily penetrated (Joest). 



Colon bacilli which have attained a higher virulence in the animal 

 body retain it for that respective species of animals. Leaving the 



