PRINCIPLES OF VETERINARY SURGERY 143 



when admitted through this avenue. Insect bites are known 

 to produce a suitable abrasion for the admission of the mi- 

 crobe into the skin, and surgical wounds made with unclean 

 instruments are not uncommon channels of infection. 



Dependent upon the avenue of entrance the bacillus an- 

 thracis produces two distinct forms of the disease.^intemal 

 anthrax and external anthrax. When ingested they pass 

 into the bowels and multiply in the form of bacillary net- 

 works around the villi and enter the blood through the ab- 

 sorbent vessels. The resulting phenomena proves fatal in 

 four to twenty-four hours. If the channel of admission is an 



Fig. 16. 

 Bacillus Anthracis. 



external breach, the grave symptoms are preceded by the 

 appearance of a large, threatening, doughy swelling that 

 does not crepitate nor manifest any tendency toward sup- 

 puration, by which it is differentiated from malignant-, 

 oedema, symptomatic anthrax and phlegmons. In the horse 

 these lesions often appear on the thigh, neck, withers and. 

 shoulders. 



Resistance. — The bacillus is noted for its resistant pro- 

 pensities. Dried spores retain their vitality for years, and 

 it requires no less than five minutes boiling to kill them. 

 They can be immersed in a five per cent solution of carbolic 

 solution for twenty-four hours, and then germinate, but 

 are killed in a short time with mercuric chloride i to i,ooo. 



