47^ iXrLL'ENCE (;!• CI.l M ATi'. i i\ ANIMAL DISKA.Si:. 



by ordinary chemical or physical germicides, aiid can only with- 

 stand dessication for a matter of days. , 



On the other liand, we know that under certain conditions 

 the bacillus is capable of giving rise to a v^egetative form known 

 as a spore, which is extremely resistant indeed. Two conditions 

 are neces.sary for the formation of these bodies; one of these 

 a supply of free oxygen, the other being a suitable temperature: 

 the optimum degree of the latter being about 30° C. although 

 their fonnation can occur at any temperature inside the minimum 

 limit of 16° C. and the maximum limit of 42° C. That they 

 are extremely resistant has been proved from their behaviour 

 when subjected to the action of the usual chemical germicides, 

 or when under the influence of [)hysical agents, such as heating 

 to a high degree, and their resistance to desiccation is remark- 

 able, inasmuch as they have been ksiovvn to survive in this dried 

 condition for over ten years. Putrefactive changes are not 

 inimical to them, and here again they differ from the bacillary 

 form, wliich is soon destroyed in the presence of these changes. 



These spores are not formed by the bacillus when it is pre- 

 sent in the bodies of animals suffering from the disease, nor are 

 they formed after the death of the animal ])rovided the carcase 

 is unopened, owing here to the lack of free oxygen necessarx 

 for their production. Under tliese latter conditions decom- 

 position occurs in the usual way, and the bacillary form of the 

 organism is soon destroyed in the presence of the putrefactive 

 changes then occurring. 



On the other liand, when the body of an animal dead from 

 the disease is opened u]) soon after <^leath, the bacilli escaping 

 with the blood and other body fluids and organ juices soon find 

 the supply of oxygen necessary for spore formation, and spores 

 are rapidly formed. If now, as very commonly happens, the 

 carcase is opened on the ])asture or veld, it is not difficult to see 

 how the soil and ])erhaps water may become infected through 

 material containing the organism and its spores. Infection of soil 

 has been known to follow the use of manures prepared from 

 contaminated hides or bones, or following irrigation by water 

 from knackeries or tanneries where infected hides had been 

 dealt with, but under natural conditions, and especially in this 

 coimtry, the commxonest method of original soil infection is prob- 

 ably that above mentioned, namely, the opening up of carcases 

 on the veld soon after death. Once the soil is infected it is 

 easy to understand how this infection is maintained through 

 the presence of the spore, which is so resistant, and which, as 

 mentioned above, is capable of surviving, even under desiccation. 

 for ten or more years. It is also believed that in warmer coun- 

 tries the organism cannot only exist in the soil, but even multiply 

 when a sufficiently suitable temperature is present. 



These facts will explain, in part, why certain areas may come 

 to be regarded as '' anthrax localities," but we must now note 

 some facts in regard to the association of the spread of the dis- 



