SCIENCE. 
1 13 
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 
being 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 ir82 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 
r8o9 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. I11 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 vent 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, 
