THE ATTRIBUTES OF MAN.
We must now consider briefly some of the attributes of man, and see if he really possesses attributes which are in no inferior degree possessed by animals. Before proceeding directly to the consideration of the attributes of man, it will be best to show the correlation that exists between what are called man's vital forces and the physical forces of nature. To do this let us choose three forms of its manifestation: these shall be heat evolved within the body; muscular energy or motion; and lastly, nervous energy or that form of force which, on the one hand, stimulates a muscle to contract, and on the other appears in forms called mental. It will not take any extensive argument to demonstrate that the heat of the body does not differ from heat from any other source. It is known that the food taken into the body contains potential energy, which is capable of being in part converted into actual heat by oxidation; and since we know that the food taken into the body is oxidized by the oxygen of the air supplied by the lungs, the heat of the body must be due to the slow oxidation of the carbon, perhaps also hydrogen, sulphur, and phosphorus in the food. Now since this so-called vital heat is developed by oxidation, is recognized by the same tests and applied to the same purposes as any other heat, it is as truly correlated to the other forces as when it has a purely physical origin. The amœboid activity of a white blood corpuscle is stimulated within certain limits by heat. Hatching of eggs and the germination of seeds may be likewise hastened or retarded by access or deprivation of heat. It was considerations such as these which led to the doctrine of correlation of the vital and physical forces.
With respect to the muscular force exerted by an animal, it was supposed that it was created by the animal. Dr. Frankland[36] says to this: "An animal can no more generate an amount of force capable of moving a grain of sand, than a stone can fall upwards or a locomotive drive a train without fuel." As the amount of CO2 exhaled by the lungs is increased in the exact ratio of work done by the muscle, it cannot be doubted that the actual force of the muscle is due to the converted potential energy of the food. Since every exertion of a muscle and nerves involves the death and decay of those tissues to a certain extent, as shown by the excretions, Prof. Orton[37] has been led to say: "An animal begins to die the moment it begins to live." "A muscle," says Barker,[38] "is like a steam-engine, is a machine for converting the potential energy of carbon into motion; but unlike a steam-engine, the muscle accomplishes this conversion directly, the energy not passing through the intermediate stages of heat. For this reason the muscle is the most economical producer of mechanical force known." The muscles which give the downward stroke of the wing of a bird are fastened to the breastbone, and their power in proportion to the weight of the bird is as 10,000 to 1. This great power is needed, for the air is 770 times lighter than water; the hawk being able to travel 150 miles an hour.
The last of the so-called vital forces under consideration, is that produced by the nerves and nervous centres. Barker says: "In the nerve which stimulates a muscle to contract, this force is undeniably motion, since it is propagated along this nerve from one extremity to the other." This force has been likened unto electricity, the gray or cellular matter being the battery, the white or fibrous matter the conductors. Du Bois Reymond[39] has demonstrated that this force is not electricity, though by showing that its velocity is only ninety-seven feet a second. The velocity varies, though, in different animals; it is, according to Prof. Orton,[40] "more rapid in warm-blooded than in cold-blooded animals, being nearly twice as fast in man as in the frog." Wheatstone, by his method, gives the velocity of electricity in copper wire at 62,000 geographical miles per second; but as neither Fizeau, Gould, Gonnelle and others could arrive at the same result, the method was shown to be incorrect, and it remained for Dr. Siemen[41] to discover the true method, which gives the velocity just one-half that of Wheatstone's estimate, or 31,000 geographical miles per second. In the opinion of Bence Jones, the propagation of a nervous impulse is a sort "of successive molecular polarization, like magnetism." But that this agent is a force as analogous to electricity as is magnetism, is shown not only by the fact that the transmission of electricity along a nerve will cause the contraction of a muscle to which it leads, but also by the important fact discovered by Marshall, that the contraction of a muscle is excited by diminishing its normal electrical current,[42] a result which could take place only with a stimulus, says Barker, "closely allied to electricity. Nerve force must therefore be transmuted potential energy." Prof. Huxley says,[43] "the results of recent inquiries into the structure of the nervous system of animals, converge toward the conclusion that the nerve-fibres which we have hitherto regarded as ultimate elements of nervous tissue, are not such, but are simply the visible aggregations of vastly more attenuated filaments, the diameter of which dwindles down to the limits of our present microscopic vision, greatly as these have been extended by modern improvements of the microscope; and that a nerve is, in its essence, nothing but a linear tract of specially modified protoplasm between two points of an organism, one of which is able to affect the other by means of the communication so established. Hence it is conceivable that even the simplest living being may possess a nervous system."
Herbert Spencer[44] says all direct and indirect evidence "justifies us in concluding that the nervous system consists of one kind of matter. In the gray tissue this matter exists in masses containing corpuscles, which are soft and have granules dispersed through them, and which, besides being thus unstably composed, are placed so as to be liable to disturbances to the greatest degree. In the white tissue this matter is collected together in extremely slender threads that are denser, that are uniform in texture, and that are shielded in an unusual manner from disturbing forces, except at their two extremities."
The last consideration is that form of force (thought power) which appears in manifestations called mental. It must be noticed at the outset, that every external manifestation of thought force is a muscular one, as a word spoken or written, a gesture, or an expression of the face always takes place; hence this force must be intimately correlated to nerve force. It is very certain, then, that thought force is capable in external manifestations of converting itself into actual motion. But here the question arises, can it be manifested inwardly without such a transformation of energy? Or is the evolution of thought entirely independent of the matter of the brain?
This question can be answered by actual experiment, strange as it may appear. Experiments have demonstrated that any change of temperature within the skull was soonest manifested externally in that depression which exists just above the occipital protuberance. Here Lombard[45] fastened to the head at this point two little bars, one made of bismuth, the other of an alloy of antimony and zinc, which were connected with a delicate galvanometer;[46] to neutralize the result of a gradual rise of temperature over the whole body, a second pair of bars, reversed in direction, was attached to the leg or arm, so that if a like increase of heat came to both, the electricity developed by one would be neutralized by the other, and no effect would be produced by the needle unless only one was affected. By long practice it was ascertained that a mental torpor could be induced, lasting for hours, in which the needle remained stationary. But let a person knock on the door outside of the room, or speak a single word, even though the experimenter remained absolutely passive, the reception of the intelligence caused the needle to swing twenty degrees. "In explanation of this production of heat," says Barker,[47] "the analogy of the muscle at once suggests itself. No conversion of energy is complete, and as the heat of muscular action represents force which has escaped conversion into motion, so the heat evolved during the reception of an idea is energy which has escaped conversion into thought, from precisely the same cause." Dr. Lombard's experiments have shown that the amount of heat developed by the recitation to one's self of emotional poetry, was in every case less when recitation was oral; this is of course accounted for by the muscular expression. Chemistry teaches that thought-force, like muscle-force, comes from the food, and demonstrates that the force evolved by the brain, like that produced by the muscle, comes not from the disintegration of its own tissue, but is the converted energy of burning carbon.[48] "Can we longer doubt," says Barker,[49] "that the brain too, is a machine for the conversion of energy? Can we longer refuse to believe that even thought force is in some mysterious way correlated to the other natural forces? and this even in the face of the fact that it has never yet been measured.[50] Have we not a right to ask 'why a special force (vital force) should be needed to effect the transformation of physical forces into those modes of energy which are active in the manifestation of living beings, while no peculiar force is deemed necessary to effect the transformation of one mode of physical force into any other mode of physical force?"
Richard Owen says:[51] "In the endeavor to clearly comprehend and explain the functions of the combination of forces called 'brain,' the physiologist is hindered and troubled by the views of the nature of those cerebral forces which the needs of dogmatic theology have imposed on mankind. * * * Religion, pure and undefiled, can best answer how far it is righteous or just to charge a neighbor with being unsound in his principles who holds the term 'life' to be a sound expressing the sum of living phenomena, and who maintains these phenomena to be modes of force into which other forms of force have passed from potential to active states, and reciprocally, through the agency of the sums or combinations of forces impressing the mind with the ideas signified by the terms 'monad,' 'moss,' 'plant,' or 'animal.'"