History of the Conflict Between Religion and Science

by John William Draper

Similarity of effects indicates similarity of causes; similarity of actions demands similarity of organs. I would ask the reader of these paragraphs, who is familiar with the habits of animals, and especially with the social relations of that wonderful insect to which reference has been made, to turn to the nineteenth chapter of my work on the "Intellectual Development of Europe," in which he will find a description of the social system of the Incas of Peru. Perhaps, then, in view of the similarity of the social institutions and personal conduct of the insect, and the social institutions and personal conduct of the civilized Indian—the one an insignificant speck, the other a man—he will not be disposed to disagree with me in the opinion that "from bees, and wasps, and ants, and birds, from all that low animal life on which he looks with supercilious contempt, man is destined one day to learn what in truth he really is."

The views of Descartes, who regarded all insects as automata, can scarcely be accepted without modification. Insects are automata only so far as the action of their ventral cord, and that portion of their cephalic ganglia which deals with contemporaneous impressions, is concerned.

It is one of the functions of vesicular-nervous material to retain traces or relics of impressions brought to it by the organs of sense; hence, nervous ganglia, being composed of that material, may be considered as registering apparatus. They also introduce the element of time into the action of the nervous mechanism. An impression, which without them might have forthwith ended in reflex action, is delayed, and with this duration come all those important effects arising through the interaction of many impressions, old and new, upon each other.

There is no such thing as a spontaneous, or self-originated, thought. Every intellectual act is the consequence of some preceding act. It comes into existence in virtue of something that has gone before. Two minds constituted precisely alike, and placed under the influence of precisely the same environment, must give rise to precisely the same thought. To such sameness of action we allude in the popular expression "common-sense"—a term full of meaning. In the origination of a thought there are two distinct conditions: the state of the organism as dependent on antecedent impressions, and on the existing physical circumstances.

In the cephalic ganglia of insects are stored up the relics of impressions that have been made upon the common peripheral nerves, and in them are kept those which are brought in by the organs of special sense—the visual, olfactive, auditory. The interaction of these raises insects above mere mechanical automata, in which the reaction instantly follows the impression.

In all cases the action of every nerve-centre, no matter what its stage of development may be, high or low, depends upon an essential chemical condition—oxidation. Even in man, if the supply of arterial blood be stopped but for a moment, the nerve-mechanism loses its power; if diminished, it correspondingly declines; if, on the contrary, it be increased—as when nitrogen monoxide is breathed—there is more energetic action. Hence there arises a need of repair, a necessity for rest and sleep.

Two fundamental ideas are essentially attached to all our perceptions of external things: they are SPACE and TIME, and for these provision is made in the nervous mechanism while it is yet in an almost rudimentary state. The eye is the organ of space, the ear of time; the perceptions of which by the elaborate mechanism of these structures become infinitely more precise than would be possible if the sense of touch alone were resorted to.

There are some simple experiments which illustrate the vestiges of ganglionic impressions. If on a cold, polished metal, as a new razor, any object, such as a wafer, be laid, and the metal be then breathed upon, and, when the moisture has had time to disappear, the wafer be thrown off, though now the most critical inspection of the polished surface can discover no trace of any form, if we breathe once more upon it, a spectral image of the wafer comes plainly into view; and this may be done again and again. Nay, more, if the polished metal be carefully put aside where nothing can deteriorate its surface, and be so kept for many months, on breathing again upon it the shadowy form emerges.

Such an illustration shows how trivial an impression may be thus registered and preserved. But, if, on such an inorganic surface, an impression may thus be indelibly marked, how much more likely in the purposely-constructed ganglion! A shadow never falls upon a wall without leaving thereupon a permanent trace, a trace which might be made visible by resorting to proper processes. Photographic operations are cases in point. The portraits of our friends, or landscape views, may be hidden on the sensitive surface from the eye, but they are ready to make their appearance as soon as proper developers are resorted to. A spectre is concealed on a silver or glassy surface until, by our necromancy, we make it come forth into the visible world. Upon the walls of our most private apartments, where we think the eye of intrusion is altogether shut out and our retirement can never be profaned, there exist the vestiges of all our acts, silhouettes of whatever we have done.

If, after the eyelids have been closed for some time, as when we first awake in the morning, we suddenly and steadfastly gaze at a brightly-illuminated object and then quickly close the lids again, a phantom image is perceived in the indefinite darkness beyond us. We may satisfy ourselves that this is not a fiction, but a reality, for many details that we had not time to identify in the momentary glance may be contemplated at our leisure in the phantom. We may thus make out the pattern of such an object as a lace curtain hanging in the window, or the branches of a tree beyond. By degrees the image becomes less and less distinct; in a minute or two it has disappeared. It seems to have a tendency to float away in the vacancy before us. If we attempt to follow it by moving the eyeball, it suddenly vanishes.