18 CHEMICAL AGJENTS AND PROTOPLASM [Ch. J 



NH - CH N . CH3 - CH 



I II I II 



CO C-NH CO C-N.CH3 



I 1 ^00 I 1 \co 



xanthin. theobromine. 



N.CH3-CH 



I II 



CO C - N . CH3 



I I >C0 



N . CH3 - C = N ^ 



coffein. 



are successively less poisonous. (LoEW, '93, p. 46.) 

 H 



I 



"\c/%c/'' 



While henzol \ \ is rather inactive, 8 grammes 



h/''\c/''\h 



I 



H 

 per day being withstood by the human organism, with the 

 replacement of the H atoms by OH the substance becomes 

 more poisonous in direct proportion to the number of H 

 atoms thus replaced. (LoEW, '87, p. 440.) Thus there fol- 

 low in order of poisonousness : — 



Phenol (or carbolic acid) and its derivatives attack unstable 

 substances, especially aldehydes, forming insoluble products. 



Phenol itself produces in the higher animals a paralysis of 

 the nerve centres. Algse die in a 1% solution after 20 to 30 



