442 
POPULAE SCIENCE EEVIEW. 
going on in living matter ; tlie otlier^ that of causing vital 
actions. That it serves the former is universally admitted, 
but that it serves the latter purpose is not generally con- 
sidered, — at least, that it does seems to be disregarded. We 
shall, therefore, here direct our readers^ attention to this 
point. 
Light entering the eye produces the sensation of vision — 
it causes a vital action : the prick of a pin on a sleeping person 
causes pain, the retraction of his body from the source of in- 
jury, his waking up, and probably outcry — it causes vital 
actions : the genial warmth of a fire causes a sensation of com- 
fort — it causes a vital action. 'Now just in like manner to 
these does food cause vital actions. It removes the sensations 
of hunger and weariness, it produces pleasm'able feelings of 
comfort through the system, and a feeling of vigour, or power 
of doing things ; it afiects the mind, so as to make things look 
brighter in prospect, awaken kindly emotions, and allay irri- 
tability of temper. It will often banish pain, and bring sleep 
to the sleepless, and to those in other ways ill who can take 
it and digest it properly, it will produce various effects in the 
form of alleviations of symptoms of the disease. 
Now the production of vital actions by a food cannot be 
the result of its other property, that of giving material to 
the system. For to afford matter wherewith to nourish the 
body is to give to the body an additional source of foiven' to 
perform its actions — ^to walk, to hold, to see, to feel : — while 
to produce such actions is to cause the body to expend its 
jjoiver ; an effect, therefore, totally distinct in kind from the 
former. 
Any substance which causes a vital action in the body is 
said to stimulate or excite. We may, therefore, say that 
ordinary food both nourishes and stimulates. Now among 
the articles of food we use, we always partake of some in 
large quantity, when compared with that in which we do 
others. Other facts being in accordance with these, we are 
led to deduce from them that those articles of which we require 
large quantities are those serving principally to nourish the 
body, and that those taken in small quantities are of them- 
selves unimportant, and possibly, even, useless, for this pur- 
pose. Then, as regards stimulation, we find that this has no 
proportion in its intensity to the nutrition which is, or can be 
supposed to be, effected. Thus we find that mustard, pepper, 
and spice, tea, coffee, tobacco, and opium, all of which are 
taken in small quantities compared with those of meat, bread, 
and potatoes, and even in minute quantities, when the small 
amount of active principles which are derived from them is 
considered with that from the nutritious substances we have 
