VACCINE-THERAPY 115 



Where one gets isolated mild attacks of diarrhoea in 

 young animals, the ordinary medicinal treatment answers 

 all practical purposes ; but when an attack affects a large 

 number of animals, with a high death-rate, prophylactic 

 and curative measures of the most up-to-date kind must be 

 adopted. 



It is in cases such as these that vaccine-therapy should 

 be used. In young animals the alimentary canal becomes 

 infected from two distinct sources — i.e., oral and umbilical. 

 To what source one can attribute the greater number of 

 cases it is difficult to hazard an opinion, but the fact that 

 both are capable channels of infection the practitioner 

 should, in investigating any outbreak, always bear in 

 mind. 



As already stated, a large variety of bacteria are to be 

 found in the intestinal canal, and it is therefore of the 

 first importance that one should ascertain what bacteria 

 are taking on a pathogenic role. 



But this is not all. Having isolated from scrapings or 

 excreta, or both, a variety of bacteria, one has to decide 

 which is the most capable of producing the disease in 

 question. Of course, this delicate point confronts the 

 immunizer in all cases of mixed infections, more or less, 

 and it must largely be left to his own individual knowledge 

 upon which data he bases his conclusions, provided they 

 are always in keeping with the general laws of bacteri- 

 ology. The B. eoli group appear under certain circum- 

 stances to develop very potent pathogenic qualities, and 

 it is probable they are the forerunners of many other 

 grave bacterial intestinal invasions. Some authorities 

 believe the pasteurella group play a most important 

 part. 



In addition to these we have the B. jpyocyaneus, B. pro- 

 teus, and streptococcus ; while we find such specific in- 

 vasions from B. tuberculosis, B. Johne, and Streptothrix 

 actinomyces. 



In the condition known as " white scour " in calves, 



