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rophyll was formed.88 Recent researches suggest that the function of chlorophyll may be wholly protective.89 The assimilative power of the protoplasm reaches its maximum in the orange and yellow rays. Now Bert has shown that the absorption band in the chlorophyll spectrum is in the exact position of this maximum.90 Hence, Gantier believes that this substance acts as a regulator of plant respiration, the greater or less amount of luminous energy thus absorbed and transformed, being utilized by the protoplasm and stored up.91 Growth and cell-division, however, are independent of orange light and hence of chlorophyll. In the higher plants, these functions are performed by a separate and deep-lying set of cells. But in the lower, the same cell discharges both functions, assimilation going on in it during the day, and growth chiefly at night.92 Sachs had already proved that the masimum growth of plants takes place just before daylight and the minimum in the afternoon. This retarding action of sunlight upon growth is as curious as it is unexpected. It now appears that in orange light plants assimilate-absorb carbon dioxide and erolve oxygen — but do not grow and are not heliotropic; while in blue light they are strongly heliotropic but do not give off oxygen.93 Chlorophyll, however, is not confined to vegetables ; infusoria, hydras, and certain planarian worms are green from the presence of this substance, and Geddes has shown that such animals, placed in the sunlight, give off a gas which is more than half oxygen.94 These cells, moreover, contain starch granules.95
A still more striking evidence of this intimate relationship has been developed by Darwin, in his researches upon insectivorous plants.96 Not only do these plants possess a mechanism for capturing insects, but they secrete a gastric juice which digests them. Nägeli has shown the presence of pepsin in yeast cells,97 and attention has lately been called by Wurtz and others to the juice of the Carica papaya which contains a pepsin-like substance capable of peptonizing fibrin completely.98 Moreover, there is the closest similarity between diastase and ptyalin ;99 and the milk of the coirtree, recently examined by Boussingault100 and found to resemble cream closely in composition, shows the presence of emulsifying agents in the vegetable kingdom analogous to those found in the pancreas of the animal.
Another most curious proof of the identity of animal and vegetable protoplasm has been given by Claude Bernard, who has shown
that both are alike sensitive to the influence of anæsthetics. 101 A sensitive plant exposed to ether no longer closes its leaflets when touched. Assimilation and growth, as well as germination, are arrested by chloroform. The yeast plant when etherized no longer decomposes sugar to produce alcohol and carbon dioxide; while the inversive and non-vital ferment still acts to convert the canesugar into glucose; precisely as under these circumstances, the diastasic ferment converts the starch of the seed into sugar. 102 By arresting anæsthetically the process by which carbon dioxide is absorbed and oxygen evolved, the true respiratory process, being less affected, now appears; and Schutzenberger has proved that the fresh cells of the yeast plant breathe like an aquatic animal.103
It would seem then that the protoplasmic life of animals is identical with that of plants; certain measure of destructive metamorphosis taking place in eachi, evolving energy and pro. ducing carbon dioxide and water. When, however, this function is examined quantitatively, its maximum is seen to be reached in the animal. While the assimilative function characterizes the plant, the destructive function distinguishes the animal. Hence it is the function of the plant to store up energy, to produce the highly complex protoplasm. This, consumed by the animal as his food, continues his existence as a living being, the energy gradually set free by its successive steps of retrogressive metamorphosis, appearing as the work which he performs. If this view be correct, it would follow that every individual substance found in the animal — save only those which result from degradation — must be found in the plant upon which it feeds, and this is the fact. The myosin which Kühne104 has shown to be the distinctive proteid of muscle, Vines has found in the aleuron grains of the lupine and the castor oil plant, along with vitellin, the special proteid of the vitellus.105 The researches of Weyl and Bischoff have proved that gluten is formed in the dough of wheat flour by the action of a ferment upon the globulin-substance or plant-myosin which it contains, 106 precisely as Hammarsten has shown fibrin is produced in the action of a similar ferment upon fibrinogen.107 Not only this; IIoppe Seyler has extracted from maize the identical substance which has been shown by Liebreich to be the essential chemical constituent of nerve tissue, protagon.
The evidence then would seem to be conclusive that, since the protoplasm of the animal is identical with that of the vegetable,
the former must be derived from the latter. Hence the animal itself, though perhaps reconstructing more or less of the protoplasm of its food, really synthesizes none of this material. No energy therefore is stored up by the animal as such. Its total protoplasmic energy exists already in its food, in which it was stored up originally by the plant. Two inferences seem naturally to follow from this conclusion : 1st, that all the properties of animal protoplasm, and of the animal organism of which it constitutes the essential part, may be studied in the protoplasm of the plant; and 2d, that hence the solution of the life-question in the Myxomycetes will solve the life-problem for the highest vertebrate.109
Another consideration which must not be left out of the account in any discussion of the life-question is the potent influence of environment. Ordinary examples of this influence pass before our eyes erery day. Heat necessitates the germination of the seed, and light causes plant assimilation. Gravity obliges the root to grow downward and the stem to ascend. Certain sensations from without excite inevitably muscular contraction; and a ludicrous idea may provoke laughter in defiance of the will. Epidemic and epizootic diseases show the dependence of function upon external conditions, and the germ theory illustrates the utter disproportionality of the cause to the effect.110 The remarkable similarity in the periodicity observed between sunspots and the weather has been extended to include the appearance of locusts and the advent of the plague.111 Even the body politic feels its influence, Jevons having established a coincident periodicity for commercial
The modern theory of energy, however, puts this influence in a still stronger light. As defined hitherto, energy is either motion or position; is kinetic or potential.113 Energy of position derives its value obviously from the fact that in virtue of attraction it may become energy of motion. But attraction implies action at a distance; and action at a distance implies that matter may act where it is not. This of course is impossible; and hence action at a distance, and with it attraction and potential energy, are disappearing from the language of science. But what conception is it which is taking its place? By what action does the sun hold our carth in its orbit? The answer is to be found in the properties of the ether which fills all space. The existence of this ether,
the phenomena of light and electricity abundantly prove. While so tenuous that Astronomy has been taxed to prove that it exerts an appreciable resistance upon the least of the celestial bodies, its elasticity is such that it transmits a compression with a well nigh infinite velocity. 114 On the one hand, Thomson has determined its inferior limit, and finds that a cubic mile of it would weigh only one thousand-millionth of a pound;115 on the other, Ilerschel has calculated that, if an amount of it equal in weight to a cubic inch of air be enclosed in a cubic inch of space, its reaction outward would be upward of seventeen billions of pounds.116 Instead of being represented as is our air, by the pressure of a homogeneous atmosphere five miles in height, such a pressure would represent just such a homogeneous atmosphere five and a half billions of miles high, or about one-third the distance to the nearest fixed star! In Herschel's own words: “Do what we will, adopt what hypotheses we please, there is no escape in dealing with the phenomena of light, from these gigantic numbers; or from the conception of enormous physical force in perpetual exertion at every point through all the immensity of space.
Now, as Preston has suggested, 118 if we regard this ether as a gas, defined by the kinetic theory that its molecules move in straight lines, but with an enormous length of free path, it is obvious that this ether may be clearly conceived of as the source of all the motions of ordinary matter. It is an enormous storehouse of energy, which is continually passing to and from ordinary matter, precisely as we know it to do in the case of radiant transmission. When potential energy becomes kinetic, the ether loses and the matter gains motion. When kinetic energy becomes potential, the lost energy of the matter is the motion gained by the ether. Before so simple a conception as this, both potential energy and action at a distance are easily given up. All energy is kinetic energy, the energy of motion. Giving now to the ether its storehouse of tremendous power, and giving to it the ability to transfer this power to ordinary matter upon opportunity, and we have an environment compared with which the strongest steel is but the breath of the summer air. In presence of such an energy it is that we live and move. In the midst of such tremendous power do we act. Is it a wonder that out of such a reservoir the power by which we live should irresistibly rush into the organism and develop the transmuted energy which we recognize in the phe
nomena of life? Truly, as Spinoza has put it, “ Those who fondly think they act with free will, dream with their eyes open."119
Such now are some of the facts and the theories to be found in the science of to-day concerning the phenomena of life. Physiologically considered, life has no mysterious passages, no sacred precincts into which the unhallowed foot of science may not enter. Research has steadily diminished day by day the phenomena supposed vital. Physiology is daily assuming more and more the character of an applied science. Every action performed by the living body is sooner or later, apparently, to be pronounced chemical or physical. And when the last vestige of the vital principle as an independent entity shall disappear from the terminology of science, the word “ Life,” if it remain at all, will remain only to signify, as a collective term, the sum of the phenomena exhibited by an active organized or organic being.
I cannot close without speaking a single word in favor of a vigorous development in this country of physiological research. What has already been done among us has been well done. I have said with diffidence what I have said in this address, because I see around me those who have made these subjects the study of their lives, and who are far more competent to discuss them than I am. But the laborers in the field are all too few, and the reasons therefor are not far to seek. One of these undoubtedly is the high scientific attainment necessary to a successful prosecution of this kind of investigation. The physiological student must be a physicist, a chemist, an anatomist and a physiologist all at once. Again, the course of instruction of those who might fairly be expected to enter upon this work, the medical students of the country, is directed toward making them practitioners rather than investigators. In the third place the importance of physiological studies in connection with zoological research is only beginning in this country to receive the share of attention it deserves. I well remember the gratification I experienced in 1873 upon receiving a letter from Professor Louis Agassiz, announcing his intention to have lectures at Penikese upon plıysiological chemistry; a new departure for those times. In this view of the case it seems very appropriate that a new subsection of this Association should be just now in process of formation. We welcome warmly the body of men who form it and we predict that from the new subsection of Anatomy and Physiology most valuable contributions will be received for our proceedings.