ANTHRAX IN ANIMALS 337 



sides these conditions there is another factor necessary to sporula- 

 tion, namely, a suitable temperature. The optimum temperature 

 tor spore production is 30 C. Koch found that spore formation 

 did not occur below 18 C. Above 42 C. not only does 

 sponilation cease, but Pasteur found that if bacilli were kept at 

 this temperature for eight days they did not regain the capacity 

 when again grown at a lower temperature. In order to make 

 them again capable of sporing, it is necessary to adopt special 

 measures, such as passage through the bodies of a series of 

 susceptible animals. 



Anthrax spores have extremely high powers of resistance. 

 In a dry condition they will remain viable for a year or more. 

 Koch found they resisted boiling for five minutes ; and dry heat 

 at 140 C. must be applied for several hours to kill them with 

 certainty. Unlike the bacilli, they can resist the action of the 

 gastric juice for a long period of time. They are often used 

 as test objects by which the action of germicides is judged. For 

 this purpose an emulsion is made by scraping off a surface 

 culture and rubbing it up in a little sterile water. Into this 

 sterile silk threads are dipped, which, after being dried over 

 strong sulphuric acid in a desiccator, can be kept for long 

 periods of time in an unchanged condition. For use they are 

 placed in the germicidal solution for the desired time, then 

 washed with water to remove the last traces of the reagent and 

 laid on the surface of agar or placed in bouillon, in order that if 

 death of the bacilli has not occurred growth may be observed 

 (see Chap. VI.). 



Anthrax in Animals. Anthrax occurs from time to time 

 epidemically in sheep, cattle, and, more rarely, in horses and 

 deer. These epidemics are found in various parts of the world, 

 although they are naturally most far-reaching where legal pre- 

 cautions to prevent the spread of infection are non-existent. 

 All the countries of Europe are from time to time visited by the 

 disease, but in some it is much more common than in others. 

 In Britain the death-rate is small, but in France the annual 

 mortality among sheep was probably 10 per cent, of the total 

 number in the country, and among cattle 5 per cent. These 

 figures, however, have been largely modified by the system of 

 preventive treatment which will be presently described. In sheep 

 ant I cattle the disease is specially virulent. An animal may 

 suddenly drop down, with symptoms of collapse, quickening of 

 pulse ami ie>piiation, and dyspnoea, and death may occur in 

 a few minutes. In less acute cases the animal is apparently 

 out of sorts, and does not feed ; its pulse and respiration are 

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