§ 1] MODIFICATION OF VITAL ACTIONS 19 



minutes; in a 0.1% solution after 3 days. Infusoria die 

 quickly in a 1% solution. Ascaris lives only 3 hours in a 

 0.5% solution. 



Resorcin (0.5 g.) is hypnotic to man; 0.085 g. per kg. is 

 fatal to dogs. Its isomer — pyrocatechin — is more active. 

 0.1% of it in spring water kills diatoms and Infusoria after 

 a few minutes, and filamentous algae in a few hours; while, 

 with resorcin. Infusoria, diatoms, and green algse live several 

 hours — even as long as 18 hours. 



By replacing one of the H atoms of phenol by COOH (or 

 carboxyl), thus producing salicylic acid, the poisonous qualities 

 are reduced. 



Hydrocyanic Acid, CNH. — The action of this substance is 

 peculiar in that, acting on the central nervous system, it is 

 in small quantities a more violent poison for Vertebrates than 

 for Invertebrates. Hydrocyanic acid acts upon aldehydes — 

 in dilute solutions upon the most unstable compounds only ; in 

 stronger concentration upon all aldehydes. Its peculiar work- 

 ing may be hypothetically explained by assuming the aldehydes 

 of the ganglion cells to be more unstable than those of other 

 cells, so that traces of CNH which do not injure other cells 

 destroy quickly the nerve cells. (LOBW.) 



The action may be shown by the equation, — 



;C = + CNH = )C— OH. 

 H/ H/ 



aldehyde. 



The degree and variety of its action may be inferred from 

 the following data, taken from LoEW ('93): Infusoria die 

 quickly in a 0.1% solution, but Ascaris resists a 3% solution 

 for 75 minutes. The resistance of the hedgehog to CNH is 

 remarkable ; five times the dose which kiUed, in 4 minutes, a 

 cat weighing 2 kg. produced in the hedgehog only a slight 

 sickness. A myriapod (Fontaria) excretes CNH when irri- 

 tated. Certain salts of CNH act as poisons ; e.g. (CN^gHg, 

 Na2Fe(CN)gN0. 



Hydric sulphide acts as a poison either by deoxidizing the 



plasma, 



H^S + = H,0 + S, 



