ON THE CHEMICAL EFFECTS OF CHLORAL HYDRATE, ETC. 121 
In bringing forward the present communication, I feel 
more and more satisfied of the importance of that mode of 
investigation which I have employed, that it is one which 
opens another avenue to the study of physiology, as well as 
leading us to the ultimate or chemical action of agents on the 
animal economy. 
Experience and observation, based on the separate and 
combined action of the above-mentioned agents, have satisfied 
me that some reliable chemical effects may be traced out re¬ 
garding other agents, whose action on this portion of the 
animal economy is as yet unknown. 
The difficulty hitherto has been to find an agent the effects 
of which either exceed or distinctly differ from those of any 
substances hitherto recognised; while, at the same time, the 
nature and probable action of the new agent should be such as 
we can trace out without encountering serious difficulty as to 
its interpretation. 
I now proceed to the demonstration of some chemical 
changes in the blood produced by means of different agents, 
the effects of which have been hitherto entirely unknown, 
and which will prove suggestive to the mind of the medical 
practitioner as soon as he shall have presented to him a 
further series of experiments carried out after the mode of 
investigation which I have endeavoured to follow, namely, the 
general action of a chemical substance on the blood with¬ 
drawn from the body, and traced out by the microscope; 
and also the investigation of the action of the same agent on 
the blood after it has circulated through the animal economy, 
having been thereby subjected to the continuous action of 
air during its passage through the lungs. In the former 
instance we obtain a general kind of action on the blood; in 
the latter, more positive or distinct effects are presented to 
our notice, as I shall endeavour to point out by-and-by. 
The examination of the blood drawn from the circulation 
% 
and subjected to the action of a chemical agent does not 
suffice to show us all that may be produced on it by that 
agent, and we need, if it is possible, to ascertain and compare 
its effects after it has circulated in the system. This is true, 
however, only to a certain extent, for w r e know that magenta 
has a remarkable effect on the blood when added to it; but 
we find no trace of its effects on that fluid when we inject it 
under the skin, or pass it into the stomach with a view to its 
absorption and subsequent action on the blood, as the experi¬ 
ments of Professor Halford go to show. 
I now pass on to the examination I have made of the action 
