40 POISONS : THEIR EFFECTS AND DETECTION. [§§ 28 , 29 . 
Of the hydroxybenzoic acids, the para- and the 3 : 4-dihydroxy- 
compounds were inactive, the 0 - and the m- active. The above are really 
minor points ; no generalisation is at present sufficiently comprehensive 
to precisely explain the facts known as to the connection between the 
chemical constitution of the tropeines and their mydriatic effect. 
§ 28. The local anaesthetic action of cocaine is associated with its 
function as an amino-alkyl ester. The collated results of various workers 
on cocaine, tropacocaine, eucaine, stovaine, alypine, lead, according to 
Pyman, 1 to the general conclusions that in amino-alkyls having local 
anaesthetic properties (1) the acyl group is usually aromatic ; (2) the 
amino group may be secondary or tertiary, and may be associated with 
simple or complex bridged ring complexes ; and (3) the alcohol group may 
be primary, secondary, or tertiary, and may separate the acyl and amino 
groups by a chain of either two or three carbon atoms. 
The pharmacologically inactive homotropine TCH 2 OH, recent 
researches 2 have shown, may be converted into active substances by 
esterification with organic acids such as benzoic, tropic, or mandelic 
acid. Homatropine tropate, e.g., (T=CH 2 .C0 2 .CH.Ph.CH 2 0H) is said to 
be as efficient a mydriatic as atropine. . 
The physiological activity of cocaine being in some way connected 
with the presence of an hydroxyl group in the y position with regard to 
the nitrogen atom in the ring, the activity of homotropine tropate is a 
proof that the transfer of the acylated hydroxyl radicle from one carbon 
atom to a fresh one may be effected without interfering with its action, 
provided that its y position to the nitrogen is retained. 
§ 29. Adrenaline. —One of the most powerful drugs in common use 
is adrenaline ; it consists of a catechol nucleus, in combination with 
/3-hydroxyethylmethylamine. Catechol causes an increase of blood- 
pressure. The amine part of the molecule has no such effect ; but the 
rise of pressure from adrenaline is “ sympathomimetic,” that is, due to 
excitation of the sympathetic nerves. Barger and Dale ( J . Physiol ., 1910) 
have shown that the rise of pressure from catechol is not due to sympatho¬ 
mimetic action, but to an action of a different type ; these investigators 
have made an important series of researches on the rise of blood-pressure 
on a large number of amines approaching adrenaline in constitution. 
(a) Aliphatic Amines. —Methyl, ethyl, and propylamine were practi¬ 
cally inactive ; w-hexylamine exercised a decided pressor effect, greater 
than those higher and lower in the series. 
(b) Aromatic Amines .—Of these, aniline benzylamine and a-phenyl- 
ethylamine had either no action or but a feeble effect. /2-phenyl- 
ethylamine Ph.CH 2 .CH 2 NH 2 was active, more so than n-hexylamine ; 
1 Loc. cit. 
2 J. von Braun and E. Muller, Ber., 1918; Chemische Werko, Greuzach ( D.R.P, 
299,806). 
