MISCELLANEOUS 221 



confers by continued use an immunity to doses which under 

 ordinary conditions would be sufficient to cause death. The 

 adjainistration of arsenic in small doses often produces a 

 plumpness and sleekness of the skin, but is attended with the 

 danger of setting up chronic poisoning. 



As an insecticide both for animal and plant parasites 

 arsenical compounds^ are largely used. They enter into the 

 composition of many dips for sheep, cattle, &c. 



Arse7iic in Dipping Compositions. — In these the arsenic is 

 usually in the soluble form of sodium arsenite. Though in 

 many commercial dips other substances are also present, in 

 the majority of arsenical dips the efficiency depends upon the 

 amount of arsenic alone. 



In South Africa particular interest attaches to the destruc- 

 tion of ticks on cattle and sheep, because of the transmission 

 of disease by ticks. According to Lounsbury's experiments 

 in Cape Colony,* it appears that to ensure the killing of 

 all ticks the solution must contain about 1 lb. of arsenious 

 oxide in 30 gallons of water — i.e., 0*33 per cent. — though for 

 practical purposes 1 lb. in 40 or 45 gallons (0*25 to 0*22 per 

 cent.) is considered by him to be sufficient. 



A preparation reported to be efficient in Queensland con- 

 tains 1 lb. in 50 gallons — i.e., 2 per cent. 



In the same paper Lounsbury concludes that the addition 

 of tar or soap to the arsenical dips has little or no effect upon 

 their poisonous qualities. 



He also gives a table from which it may be inferred 

 that two well known arsenical dips, Demuth's and Alder- 

 son's, contain about 11 and 46 per cent, of arsenious oxide 

 respectively, and that when diluted in accordance with 

 the makers' directions — viz., 1 lb. to 6 gallons and 1 lb. 

 to 14 — they yield a liquid containing arsenious oxide in 

 the proportions of 1 lb. to 65 gallons and 1 lb. to 30 gallons 

 respectively. 



He also states that " Scrub exterminator," crude arsenite of 

  Cape Agricultural Journal, March 1905, p. 390. 



