sable as it is for us to understand the arrangements which 
they adopt, and the places which the objects we wish to 
examine occupy in the scheme of nature, do not embrace 
all that is requisite respecting the substances we have to 
employ as medicines, even independent of their uses as such. 
For those which we find most useful as remedies may occupy 
little of the attention of the naturalist ; as we only employ 
them when they have ceased to be of use to the objects 
of his care ; or at least they may never engage his notice in 
the way in which we view them. A knowledge of natural 
bodies implies also an acquaintance with their physical 
states and chemical composition. The former consists 
in the examination of such properties as their hardness, 
elasticity, specific gravity, powers of electricity or 
refraction ; all principal objects of attention in Natural 
Philosophy, a science which should form a part, not only of 
professional, but of general education. As students of 
medicine, I know not how the admirable mechanism of the 
human body, the circulation of its fluids, or the effects of 
atmospherical vicissitudes with respect to temperature, 
density, or moisture, as affecting especially the functions of 
respiration and perspiration ; or the general effects of bght, 
heat, and electricity on the human system, can be well 
understood, unless we study these general powers, and see 
how they control or affect almost every function. For if 
we do not understand their operation on the animal eco- 
nomy, when in a state of health, we are not likely to 
do so when we wish to employ them as general remedies in 
disease. These great powers, heat, light, electricity, and 
magnetism, come under the cognizance of the chemical, 
as well as of the natural philosopher, though in somewhat 
different points of view ; the former considering them more 
as agents effecting changes, and the latter as great prin- 
ciples of nature and powers in motion. 
