52 
Proceedings of the Royal Society 
of extract, separately, for each experiment. This extract is hygro- 
scopic, which further required that it should be dried and kept in 
vacuo over sulphuric acid. The greatest number of the experi- 
ments were made with the common frog (Rana temporaria ), birds, 
and various mammals. It was found that fatal results were pro- 
duced with the smallest quantity on birds, and that the largest 
doses, in proportion to weight, were required by amphibia. A dose 
of one-sixteenth of a grain proved rapidly fatal to a pigeon, whereas 
three grains have been recovered from by a frog — a quantity suffi- 
cient to produce death in a dog of average size. 
The immediate causes of death in birds and mammalia were 
found to be syncope and asphyxia, or a combination of the two ; 
and a marked connection was observed between the dose and its 
rate of absorption, and the preponderance of one or other of these 
effects. In frogs, the cardiac and respiratory functions were rapidly 
affected, but complete destruction of all the vital functions of the 
animal never occurred for many hours. This slowness in the pro- 
gress of the effects from one system to another, constituted the 
peculiar advantage of employing this animal in the research, as, 
thereby, it was possible distinctly to determine the sequence of the 
phenomena. In animals of a higher type, the implication of one 
system so rapidly influences the others, that symptoms follow each 
other with such speed as to increase very greatly the difficulties of 
a clear apprehension. 
The following are the conclusions of the investigation. 
A. Action through the Blood. 
1. Physostigma proved fatal to every animal hitherto examined, 
with the single exception of the Esere moth. Death is most rapidly 
caused in birds and mammals by the injection of the poison into 
the circulation, or when it is brought in contact with a wounded 
surface. It follows nearly as quickly when Calabar bean is in- 
troduced into a serous cavity, and much less rapidly when intro- 
duced by the mucous membrane of the digestive system. In 
rabbits, death has been caused by its application to the Schnei- 
derian, auditory, and conjunctival mucous membranes. The skin 
of frogs resists its effects for a long time, but, if applied for a suffi- 
cient period and with proper precautions, distinct evidence of its 
