38 POISONS : THEIR EFFECTS AND DETECTION. [§ 2 7 . 
2. Entrance of a chlorine atom exalts the toxic character of the 
catalytic poisons (Loew’s catalytic poisons are alcohols, ether, chloroform, 
chloral, carbon tetrachloride, methylal, carbon disulphide, and volatile 
hydrocarbons). 
3. Entrance of hydroxyl groups in the catalytic poisons of the 
fatty series weakens toxic character ; on the other hand, it exalts the 
toxicity of the substituting poisons. (Examples of Loew’s class of 
“ substituting ” poisons are hydroxylamine, phenylhydrazine, hydric 
cyanide, hydric sulphide, aldehyde, and the phenols.) 
4. A substance increases in poisonous character through every 
influence which increases its power of reaction with aldehyde or amido 
groups. If, for example, an amido or imido group in the poison 
molecule be made more “ labile,” or if thrice-linked nitrogen is converted 
into nitrogen connected by two bands, whether through addition of 
water or transposition (Umlagerung), or if a second amido group enters, 
the poisonous quality is increased. Presence of a negative group may 
modify the action. 
5. Entrance of a nitro group strengthens the poisonous character. 
If a carboxyl or a sulpho group is present in the molecule, or if, in 
passing through the animal body, negative groups combine with the 
poison molecule, or carboxyl groups are formed in the said molecule ; 
in such cases the poisonous character of the nitro group may not be 
apparent. 
6. Substances with double carbon linkings are more poisonous than 
the corresponding saturated substances. Thus neurine with the double 
linking of the carbon of CH 2 is more poisonous than choline; 
vinylamine than ethylamine. 
CH=CH„ 
(CH 3 ) 3 N 
\0H 
Neurine. 
/CH 2 —CH,OH 
(CH 3 ) 3 N< 
\OH 
Choline. 
ch 2 
II' 
ch.nh 2 
Vinylamine. 
CH 3 
I 
ch 2 .nh 2 
Ethylamine. 
§ 27. Physiological Action of the Tropeines.— The mydriatic action 
of the derivatives of the acyl derivatives of the amino-alcohol tropine 
has been studied with great thoroughness by Pyman, Jowett, Dale, and 
Marshall, and throws great light on the relation between physiological 
action and chemical constitution. 1 
1 See Jowett, Pyman, and Dale, 1th Inter. Gongr. Appl. Chem., 1909; Pyman, 
“ The Relation between Chemical Constitution and Chemical Action,” Journ. Chem. 
Soc., Trans., 1917. 
