PREVENTIVE MEDICINE 251 



common is also evidenced by the fact that the incidence of anthrax 

 does not run parallel with the use of such manures, e.g., in propor- 

 tion to its cattle population Aberdeen has 15 times as much anthrax 

 as Ayr, whereas there is no reason to suppose that less bone 

 manure is used in the latter county. In a further proportion of 

 outbreaks, infection can be traced to a previous case of the disease, 

 the ground having become grossly contaminated by blood or excre- 

 tions containing the virus. That the incidence of anthrax is as a rule 

 not dependent upon previous cases has been shown by Stockman, 

 who has remarked on the fact that in 83-5 per cent, of outbreaks 

 covering a period of 5 years (1902 to 1906) the disease had not 

 previously existed on the farm, and it does not follow that in the 

 remaining 16-5 per cent, the source of infection was a previous 

 case. From the records of 12 years (1895 to 1906) it appeared 

 that in only 4-6 per cent, of cases had the disease occurred a 

 second time during any one year upon the same farm.* 



It therefore follows that the infection of animals can be 

 divided into two groups (a) those which are in a sense accidental, 

 and the prevention of which is very difficult if not largely impos- 

 sible; and (6) those in which infection spreads from the original 

 case to other animals owing to carelessness or ignorance and is 

 therefore preventable. As stated above, the chief sources of 

 infection in the first group are imported feeding stuffs and, to a 

 less extent, artificial manure. Refuse and drainage from wool 

 factories and tanneries cause annually a few cases. The following 

 notes, taken from the annual report of the Chief Veterinary Officer 

 of the Board of Agriculture for 1915 will convey some idea of 

 the more common sources of origin. For 438 outbreaks on 

 previously clean premises, the following were regarded as the prob- 

 able sources of infection : 



(1) Effluent from tanyards getting into 



streams ..... 4 outbreaks 



(2) Sewage on pastures .... 



(3) Feeding of carcase offal to pigs 5 



(4) Use of imported feeding stuffs . . 265 



(5) Use of artificial manure on the land . 41 



(6) Use of both artificial manure and feed- 



ing stuffs . . . . 70 



(7) A recent death, not reported, but not 



improbably anthrax . . . 6 ,, 



(8) No explanation obtainable ... 42 

 Sporadic cases of anthrax, when due to the use of foodstuffs 



*Journ. Comp. Path., 1911, Vol. XXIV., p. 103. 



