198 Mr. Brodie on the different Modes 
insensible to the stimulus of the blood, and stopping the circu- 
lation. The heart beats feebly and irregularly before either the 
functions of the mind, or the respiration appear to be affected. 
Respiration is performed even after the circulation has ceased; 
and the left side of the heart is found after death to contain 
scarlet blood, which never can be the case, where the cause 
of death is the cessation of the functions of the brain or lungs. 
The convulsions, which occur when the circulation has nearly 
ceased, probably arise from the diminution of the supply of 
blood to the brain, resembling those, which take place in a 
person, who is dying from haemorrhage. 
There remains an interesting subject of inquiry, “ through 
what medium do poisons influence the brain when applied to 
wounds ?” That poisons applied in this manner do not produce 
their effects precisely in the same way as poisons taken inter- 
nally, is rendered probable by this circumstance ; that, some 
poisons, which are very powerful when applied to wounds 
even in small quantities, are either altogether inefficient when 
taken internally, or require to be given in very large quantities, 
in order to produce their effect, and vice versa. 
A poison applied to a wounded surface may be supposed to 
act on the brain in one of three ways, 
1. By means of the nerves, like poisons taken internally. 
2. By passing into the circulation through the absorbent 
vessels. 
g. By passing directly into the circulation through the 
divided veins. 
Exp. 25. In order to ascertain whether the woorara acts 
through the medium of the nerves, I exposed the axilla of a 
rabbit, and divided the spinal nerves supplying the upper 
