80 BACTERIOLOGY. 



disinfecting power of cresol with the purifying 

 power of the alkalies. 



Salicylic acid (C 6 H 4 COOH.OH), is also a 

 powerful disinfectant. The structural formulae 

 of the substances just discussed, phenol, cre- 

 sol, salicylic acid and the phenol sulfonic acids, 

 prompt the conjecture that disinfective power 

 stands in relation to the complexity and react- 

 ivity of the atom groups in the molecule. For 

 we may anticipate that these reactive atom 

 groups can interlock with and upset the atom 

 groups of the unstable proteid molecule more 

 easily than can less mobile atom groups. It 

 might be fairly expected that with the 

 entrance into chemical bodies of such atom 

 groups as exalt the reactive character of these 

 bodies, a poisonous effect would become mani- 

 fest. Phenol or mono-oxy-benzol (C 6 H 5 OH), 

 therefore, should be less poisonous than di- 

 oxy-benzol (C 6 H 4 (OH) 2 ), which in its turn 

 should be less so than tri-oxy-benzol (C 6 H 3 

 (OH) 3 ). Now the ortho-di-oxy-benzol or pyro- 

 catechin, the analogous meta-compound or re- 

 sorcin, and the paracompound or hydrochinon, 

 are, indeed, to be regarded as poisonous, but 

 not as more poisonous than phenol. The same 

 thing holds true of the tri-oxy-benzol s, among 

 which pyrogallol, oxy-hydrochinon and phloro- 

 glucin may be looked upon as less poisonous 



