511 
of Edinburgh, Session 1870 - 71 . 
It is, therefore, remarkable that the gf-g-ths °f a grain can prevent 
a dose of physostigma, equal to the minimum fatal, from causing 
death, and that the y^th of a grain is capable of rendering non- 
fatal a dose of physostigma, equal to three and a-half times the 
minimum fatal. 
Excepting dilatation of the pupils, these minute doses of atropia, 
and indeed any dose capable of antagonising the lethal action of 
physostigma, are unable to produce any symptom recognisable 
by a mere inspection of the animal. Still, they undoubtedly 
produce energetic physiological effects — effects, however, which it 
is unnecessary to describe in this brief abstract. It is sufficient to 
point out that the notion, which exists in many quarters, that 
rabbits can scarcely be affected by atropia is an erroneous one. 
Without referring to the other results obtained in his investiga- 
tion, the author pointed out, in conclusion, that unless the anta 
gonism between any two active substances be examined in the 
manner indicated in this communication, no satisfactory proof of 
its existence can be obtained. The superficial area of the region 
should always be defined, otherwise indications of antagonism 
obtained by one observer will be liable to be discredited by those 
who subsequently examine the subject. The first observer may 
succeed in performing an experiment within the area of successful 
antagonism, and thus feel satisfied of its existence ; but his suc- 
cessors may fail in obtaining any proof by so varying the dose 
of one or other substance as to pass the limits of the region of suc- 
cess (see diagram). Feeling assured that many examples of success- 
ful antagonism, besides the one he had the honour of bringing before 
the Society, will yet be discovered, the author could not avoid the 
conclusion that the imperfect methods of investigation hitherto 
pursued are accountable for the absence of success that has attended 
the numerous researches made on this subject — a subject, it need 
scarcely be added, of the greatest importance to toxicology and to 
scientific therapeutics. 
