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ENVIRONMENT 241<br />
To take other examples. Wholesome food administered to a healthy animal produces no discomfort in the<br />
stomach or alimentary canal. The feeling engendered is one of comfort and satisfaction, and not of irritation or<br />
pain. Administer to the same animal an irritating drug and soon the stomach and bowels are in an agony of pain.<br />
In such a case there is the artificial stimulation (the drug) and the consequent irritation or pain produced by the<br />
action of the drug. But (and here comes the crux) neither the stimulation nor the irritation are natural, and they<br />
do not exist in the normal condition.<br />
The muscular twitching and rigid tetanic condition produced by the continuous administration of strychnine<br />
is not normal muscular action ; neither is the relaxed, flabby muscular condition produced by the inhalation of<br />
chloroform. The strychnine unnaturally exalts the muscular function, and the chloroform unnaturally depresses<br />
it. Similarly, the brain may be excited by the drinking of alcohol and other stimulants, or it may be calmed and<br />
soothed by the administration of opium and other narcotics. Neither the alcohol nor the opium produces a per-<br />
fectly healthy brain function. The stimulant, as a matter of fact, produces the irritation and excitement which<br />
are otherwise non-existent.<br />
If nature is to be studied satisfactorily she must be watched in her simple, normal manifestations, and not in<br />
her abnormal, complex conditions, when she is hacked about and tortured by various external stimuh.<br />
The simplest plants and animals (by preference the transparent ones) yield the best results.<br />
In making these remarks I have no desire to disparage the important results obtained by a judicious use of<br />
vivisection. These have been at once interesting, instructive, and useful. Neither do I wish to set aside the<br />
valuable results obtained by cUnical research in cases of disease ; disease acting as a distorted mirror to health.<br />
My object is to distinguish between the natural operations and functions of plants and animals, in which neither<br />
irritability nor stimulation is present, and the abnormal functions of plants and animals, where irritability and<br />
stimulation are artificially induced, or are a consequence of disease.<br />
In the case of cell plants and animals where next to no differentiation obtains, the various functions of feeding,<br />
assimilating, excreting, and reproducing are performed in the simplest manner, as apart from irritabihty and stimu-<br />
lation. The lowest plant and animal forms are sensitive, and act spontaneously in certain directions—that is, they<br />
are not controlled to any extent by outside influences. What is true of plants and animals is also true of tissues<br />
and organs. The involuntary muscles in animals, on which so much depends—say the cardiac, respiratory, and<br />
ahmentary muscles—are not, in the normal condition, irritable or jogged into activity by stimuh. On the contrary,<br />
they are independent, self-acting structures, whose functions are to take in, retain, and transmit blood, air, and food<br />
respectively. The blood does not act as a stimulus to the heart, the air to the lungs, and the food to the alimentary<br />
canal. If the blood, air, and food acted as stimuli they could not be retained, as well as taken in and given out at<br />
intervals or rhythmically. The secretory and excretory organs also act spontaneously and independently. Secretion<br />
and excretion go on so long as the body is in a healthy condition. The muscles, glands, and other structures form<br />
part of a Uving mass, and every part of the mass discharges its own particular function, separately and conjointly,<br />
as apart from irritability and extraneous stimulation. The combined action of the mass represents the hfe and<br />
aggregate endowments of the individual. On the spontaneous, independent action of the units depends the<br />
integrity and well-being of the plant and animal ahke. If plants and animals had to depend for their existence on<br />
an elaborate system of artificial stimulation, it goes without saying that mishaps and accidents of the most serious<br />
character would continually occur. As a matter of fact, the so-called vegetative functions of animals are, for the<br />
wisest of purposes, placed beyond the control of the animals. The involuntary functions of the body are, in a<br />
sense, more important than the voluntary ones. They are so, as far as mere hfe is concerned.<br />
§ 47. Environment.<br />
The subject of environment is closely associated with the theory of irritability and artificial stimulation. It<br />
is held by many that environment furnishes a stimulus which causes plants and animals to modify their constitu-<br />
tions, their organs, and their general shape and appearance throughout the ages, and makes them what they are at<br />
the present day. It is even asserted that environment produces the sense organs and the organs of locomotion.<br />
According to this view, environment is a leading factor in the production of every conceivable difference in<br />
plants and animals ;<br />
plants and animals being regarded as living plastic things, which are acted upon by their sur-<br />
roundings nolens vokns, or in spite of themselves. Environment is vaunted as superior to plants and animals ;<br />
these being, at best, mere living automata, with no discriminating or directive power at their disposal. The dead<br />
surroundings are supposed to shape and determine the destinies of living plants and animals respectively. The<br />
theory is the invention of the mechanical school of physiologists. According to this school externahties form the<br />
skin with its sensory nerves ; odoriferous substances the sense of smell ; sapid substances that of taste ; sound that<br />
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