100 VETEEINAEY TOXICOLOGY 



tion the ferric salts present yield, with the ferrocyanide, 

 Prussian blue. It has been shown^ that the delicacy of 

 this test reaches the sirffir part of a grain ; of equal delicacy, 

 but not characteristic, is the production of a more or less 

 dark yellow to red-brown coloration by warming with 

 alkaline picrate. By the aid of these tests prussic acid 

 may be detected post-mortem, not only in the viscera, but 

 also in the blood and brain. It is interesting to observe 

 that in the case of a rabbit killed forty minutes after the 

 administration of a non-toxic dose of #„ grain by the 

 mouth, cyanide was present in the stomach, but could not 

 be recognised either in the blood or brain. 



REFERENCES TO HYDROCYANIC ACID. 



1 Mosselmann, Vet. Jl, 1908, p. 265. 



2 C. Aggio, Vet. JL, 1907, p. 599. 



3 McCall, Vet. Becord, 1906, p. 776. 



* Damman and Behrens, Vet. JL, 1906, p. 396. 



^ P. Adsetts, Veterinarian, 1871, p. 336. 



^ Dunstan and Henry, Journal of Board of Agriculture, 



1907-08, p. 726. 

 ^ Lander, Journal of Board of Agriculture, 1910-11, p. 904, 

 " Lander and Walden, Analyst, 1911, p. 266. 

 " J. T. Dumphy, Transvaal Agricultural Journal, 1905-06, 



p. 315. 



CARBOLIC ACID AND ALLIED PREPARATIONS. 



Sources and Preparations.— CarJoZic acid [phenol 

 (CsHgOH)] is a constituent of the tar either of coal or wood. 

 The proportion of carbolic acid in crude coal tar is about 

 0"5 per cent., and it is separated in the distillation in 

 the so-called middle oil. The three isomeric cresols 

 (C6H4CH3OH) — ortho, meta, and para respectively — form 

 about 3 per cent, of the heavy or creosote oil of tar 

 distillation. In wood tar there is also found guaiacol 

 (C6H40CH30H),the methyl ether of orthodihydroxybenzene. 

 Of these various phenols, carbolic acid is the only one prepared 



