SCIENCE. 



113 



over so broad a surface that in places it must be danger- 

 ously thin. It is, therefore, with a very keen sense of the 

 temerity involved in the undertaking, that I ask your atten- 

 tion during the hour allotted me, to some points which ap- 

 pear to me to have been recently gained in the discussion 

 of the question of life. 



My friend and predecessor, Professor Marsh, opened his 

 excellent address at Saratoga with the question " What is 

 Life?" In a somewhat different sense I too ask the same 

 question. But I fear it is only to echo his reply, " the an- 

 swer is not yet." The result, however, cannot long be 

 doubtful. " A thousand earnest seekers after truth seem 

 to be slowly approaching a solution." And though the ig- 

 nis fatuus of life still dances over the bogs of our misty 

 knowledge, yet its true character cannot finally elude our 

 investigation. The progress already made has hemmed it 

 in on every side ; and the province within which exclu- 

 sively vital acts are now performed, narrows with each year 

 of scientific research. 



What now are we to understand by the word " Life " in 

 this discussion ? A noteworthy parallel is disclosed in the 

 progress of human knowledge between the ideas of life and 

 of force. Both conceptions have advanced, though not with 

 equal rapidity, from a stage of complete separability from 

 matter to one of complete inseparability. Life is now uni- 

 versally regarded as a phenomenon of matter, and hence of 

 course, as having no separate existence. But there still 

 exists a certain vagueness in the meaning of the term " life." 

 Two distinct senses of this word are in use ; the one meta- 

 physical, the other physiological. The former, synonomous 

 with mind and soul, at least in the higher animals, has been 

 evolved from human consciousness ; the latter has arisen 

 from a more or less careful investigation of the phenomena 

 of living beings. It need scarcely be said that it is in the 

 sense last mentioned that the word " life " is used in science. 

 The conception represents simply the sum of the phen- 

 omena exhibited by a living being. 



Moreover, the progress which has been made in the solu- 

 tion of the life-question has been gained chiefly by inves- 

 tigation of special functions. But the functions of a vital 

 organism are themselves vital. What then is the meaning 

 of " vital " as applied to a function? Fortunately the an- 

 swer is not difficult. " Life," says Kiiss, the distinguished 

 Strasbourg physiologist, " is all that cannot be explained by 

 chemistry or physics." Guided by such a definition the 

 work of the physiological investigator is simple. He has 

 only to test each separate operation which he finds going 

 on in the organism and to declare whether it be chemical or 

 physical. If it be either, then since each function is non- 

 vital, the entire organism must be non-vital also. Hun- 

 dreds of able investigators, provided with the most effective 

 appliances of research, are now in full cry after the life prin- 

 ciple. Naturally, a vast amount of collateral knowledge is 

 accumulated in the process. The quantitative as well as 

 the qualitative relations of things are fixed, and many im- 

 portant facts are collected. 



With the object in view thus clearly defined, we are not 

 surprised that great progress has been made. A vital pro- 

 cess, like the catalytic ones of the older chemistry, was 

 found by such research to be simply a process which, for 

 want of sufficient investigation, is not yet understood. 

 While therefore, undoubtedly, much work yet remains to 

 be done in the realm still called vital, the prophetic vision 

 is already bright which will witness the last traces of inex- 

 plicable phenomena vanish and the words expressing them 

 relegated to the limbo of the obsolete. 



As a first result of recent work, the living organism has 

 been brought absolutely within the action of the law of the 

 Conservation of Energy. Whether it be plant or animal, 

 the whole of its energy must come from without itself 

 Deing either absorbed directly or stored up in the food. 

 An animal, like a machine, only transforms its energy. 

 Lavoisier's guinea-pig, placed in the calorimeter, gave as 

 accurate a heat-return for the energy it had absorbed in its 

 food, as any thermic engine would have done. But the 

 parallel goes further. The mechanical work of an engine 

 is measured by the loss of its heat and not of its substance. 

 So the mechanical or intellectual work of a living being is 

 measured by the amount of food rather than the amount of 

 tissue which is burned. The energy evolved daily by the 

 human body would raise it to a height of about six miles. 



But beside heat, work may be the out come of the organ- 

 ism ; and this through the agency of the muscles. Their 

 absolute obedience to mechanical law in their mode of ac- 

 tion has been admirably established by Haughton. The 

 work a. muscle does, it does in contracting. It is to the 

 mechanism of muscle-contraction that we are indebted for 

 another illustration of our subject. 



When work is done by a muscle in contracting, three 

 changes are observed to take place in its tissue. First, 

 there is a loss of its electric tension ; second, there is an 

 evolution of heat in it ; and third, carbon dioxide appears 

 there, and its reaction, before neutral, becomes acid. 



Matteucci was the first to observe and to call attention to 

 the remarkable similarity in structure and in the mechanism 

 of operation, between striated muscular fibre and the elec- 

 tric organ of certain fishes. Recently, Marey has repeated 

 and extended his observations. In structure, the electric 

 organ is made up, like the muscle, of columnar masses 

 each separable transversely into vesicular sections. In a 

 torpedo weighing seventy-three pounds, there were 1182 of 

 these columns, with 150 sections, on an average, in each, 

 In the muscles which bend the fore-arm, there are 798,000 

 fibrillae. As to the mechanism, alike in muscle and in 

 electric organ, an electric current stimulates action on 

 opening and on closing the circuit, but not when it is flow- 

 ing ; the same phenomena takes place in both with the di- 

 rect and with the inverse current ; both are reflex ; stimu- 

 lation of the electric nerve produces discharge, as that of 

 the motor nerve causes muscular shock ; an entire paral- 

 ysis follows nerve-section ; curare paralyzes both ; and te- 

 tanus results in both from rapid currents or from strych- 

 nine. 



Still more striking analogies are furnished by the investi- 

 gation of the susurrus or muscular sound, first noticed in 

 1809 by Wollaston. This sound is produced by all mus- 

 cles when in the state of contraction, the pitch of the note 

 being not far from thirty vibrations per second. It is evi- 

 dently only the intermittent discharge of the muscular fibre. 

 A single excitation produces a muscular shock. As this 

 production requires from eight to ten hundredths of a sec- 

 ond, it is evident that if another stimulus be applied before 

 the first has disappeared the two will coalesce ; and when 

 twenty per second reach the muscle it becomes perma- 

 nently contracted or tetanized. By means of a very sensi- 

 tive myograph, Marey has found that in voluntary contrac- 

 tion the motor nerves are the seats of successive acts, each 

 of which produces an excitation of the muscle. Li 1877, 

 Marey examined similarly the discharge of the torpedo and 

 found a most complete correspondence between it and 

 muscular contraction. Since electric tension disappears 

 from a muscle during contraction, is not the evidence con- 

 clusive that muscular contraction, like the discharge of the 

 electric organ of the torpedo, is an electrical phenomenon? 



Granting electric discharges to be the cause of muscle-con- 

 traction, what is its origin? That it is not carried to the 

 muscle by the nerves follows from the fact that a muscle 

 will still contract when deprived of all its nerve-fibres. It 

 must therefore be generated within the muscle itself. To 

 reach a solution of the problem we must obviously follow 

 the analogies of its production elsewhere. 



Perhaps no single question in physics has been more 

 keenly discussed than this one of the origin of electric charge. 

 The memorable conflict between Galvani and Volta, between 

 animal electricity and the electricity of metallic contact, suc- 

 ceeded by the even more triumphant overthrow of the latter 

 and the establishment ultimately by Faraday, of the electro- 

 chemical theory ; 'these are facts fresh in all our memories. 

 The justice of time however in this case, if it has been tardy, 

 has been none the less sure. The experiments of Thomson 

 have vindicated Volta and established the contact theory as 

 a vera causa. And more curiously still, it now appears to 

 be proved that both contact and chemical action underlie 

 the production of that very animal electricity so stoutly bat- 

 tled for by Galvani and his associates. 



Volta's experiments to prove that a difference of potential 

 is developed by the contact of two heterogeneous metals 

 were not crucial. But Thomson, repeating them with the 

 aid of more delicate apparatus, has shown that whenever 

 copper and zinc are brought in contact, the copper becomes 

 negative to the zinc. In proof that the chemical action of 

 atmospheric moisture was not the cause of the phenomenon, 



