556 THE BACILLUS OF QUARTER ILL 



Discrete colonies. Small whitish spheres with lateral offshoots appear in 

 the depth of the gelatin which subsequently become cloudy and irregular 

 in shape. Gas is formed and the gelatin liquefied. 



Agar. Deep stab cultures. When incubated at 37 C. a cloudy whitish 

 line rapidly appears along the line of the stab, the agar is then broken up 

 by the gas evolved and the gaps are invaded by the culture. 



Potato. No apparent growth. 



Milk. Abundant growth. 



White of egg. White of egg is not sensibly attacked ( Jungano and Distaso). 



SECTION HI. BIOLOGICAL PROPERTIES. 

 1. Vitality and virulence. 



The bacillus of quarter ill has considerable vitality and since it forms 

 spores is able to resist the ordinary methods employed for the destruction of 

 micro-organisms. In cultures, the spores resist a temperature of 100 C. for 

 several minutes. If some of the exudate in the muscles be dried the spores 

 can only be killed by exposure to moist heat at 110 C. for several hours. 

 Ordinary antiseptic solutions and putrefactive changes have no action on 

 the spores. 



The virulence of the organism disappears somewhat rapidly in culture : 

 after being sub-cultivated five or six times in broth it fails to set up a fatal 

 disease in guinea-pigs. Its virulence in culture is readily destroyed by physical 

 agents, e.g. an exposure to a temperature of 100 C. for 2 minutes renders it 

 a virulent : serum cultures are more resistant than broth cultures. 



In the dried exudate from swellings on the other hand the virulence is as 

 persistent as the vitality ; in such an exudate the bacilli after being dried 

 at 35 C. will remain alive and virulent for years. They are able also to 

 resist exposure to high temperatures for several hours (see under Vaccina- 

 tion, infra). 



In the living tissues the organism retains its properties for a long time : e.g. if 

 a frog which has been inoculated but has resisted infection be left for a fortnight 

 or 3 weeks and then be put in the incubator at 25 C. it will suffer from the disease 

 (Arloing). 



2. Vaccination. 



One attack of symptomatic anthrax confers immunity, and the disease 

 does not recur in the same subject. 



1. The injection of the virus into the veins of an ox, a harmless proceeding 

 if properly done, will render the animal immune (Arloing, Cornevin, and 

 Thomas). Cattle can be vaccinated by inoculating 5 or 6 c.c. of a virulent 

 exudate into the jugular vein but on account of inherent difficulties and 

 dangers it has been abandoned as a practical method of vaccination. 



(ii) The principle of a method of vaccination devised by Arloing, Cornevin 

 and Thomas is the inoculation of an attenuated virus into the tip of the tail. 

 It has already been mentioned that inoculation in this situation is not a 

 severe method of infection. The attenuated virus is prepared by exposing 

 dried serous exudate from -the muscles to the action of heat as follows : 



The infected muscles of an ox or sheep dead of quarter ill are finely minced and 

 added to two-thirds their weight of sterile water. The mixture is rubbed up in a 

 mortar and filtered through muslin : the filtrate is poured on to porcelain plates 

 and kept in a dry incubator at 35 C. until completely dry, after which the dried 

 extract is ground up in a pepper mill and then in a mortar until reduced to a very 

 fine powder. In this way a very virulent product is obtained which retains its 

 toxicity for years. 



