102 VETEEINAEY TOXICOLOGY 



ing may arise ; and under this general heading must also 

 be included cases of poisoning due to the contamination of 

 water by coke oven and gasworks effluents. 



As regards tar, it must be remembered that crude tar 

 contains some 3 per cent, of cresols or tar acids, nearly all 

 of which passes into water when the tar and water are 

 mixed with one another. In a similar way water may take 

 up sufficient cresols from creosoted sleepers to cause 

 poisoning. But creosote, as it contains a larger proportion 

 of cresols, is naturally more dangerous than crude tar. Cases 

 of poisoning by both these means have been investigated. 



Effluent waters from coke ovens and gasworks contain 

 sulphoeyanides and tar acids. An example of a coke oven 

 effluent, analysed in 1909, showed : 



Sulphocyanide ... ... ... 1'82 grains per gallon. 



Cresols (tar acids) ... ... 5'81 „ ,, 



Large quantities of such a water would be required to 

 cause death. Nevertheless, an effluent of such composition 

 must be regarded as a dangerous contamination to drinking- 

 water. 



Wallis Hoare saw a case of a cow (poisoned by effluents 

 from a disinfectant factory) in which the milk smelled 

 of carbolic acid, as also did the dejecta. Eecovery after 

 purgation and olive oil took place slowly. 



Toxicity. — The toxicity of phenol varies according to the 

 channel of absorption. The lethal dose for the horse by 

 the alimentary tract is about 1 ounce, for the dog from 

 1 to 2 drachms, although 15 grains is said to have caused 

 death. 



Of the cresols, the ortho compound is more poisonous 

 than carbolic acid, para-cvQ^ol still more so, but mete-cresol 

 less. All the phenols thus appear to be powerful poisons 

 of the same order as hydrocyanic acid and arsenic. It is ex- 

 ceedingly difficult — in fact, impossible — to give quantitative 

 data regarding poisoning by absorption through the skin, 

 but in the case of creosotic sheep-dips the Departmental 

 Committee found that a 1| per cent, tar acid dip caused 



