SCIENCE. 



supposition the whole operation of this labor consisted 

 exclusively in the development of heat. The burning of 

 one kg. of coal may serve as an example ; if no other 

 effects are accomplished, about 8000 units of heat will be 

 released. The work which the kindred powers between 

 the atoms in one kg. of coal and the two-fold number of 

 atoms of oxygen accomplish in their union into carbonic 

 acid, thus amounts to 8000 x 425 or 3,400,000 kilogram- 

 meters. From this an idea may be formed of the prodig- 

 ious intensity of the chemical power of attraction between 

 an atom of carbon and an atom of oxygen. The force 

 with which the particles of carbon, amounting only to 

 one kg., rush from a very little distance to the corres- 

 ponding particles of oxygen in burning, is precisely as 

 great as when a body weighing 3,400,000 kilograms falls 

 from a height of 1 m. 



Let us go back with these axioms from natural phi- 

 losophy in general to muscular action. If, as was shown, 

 there are chemical powers of attraction, whose operation 

 or performance of labor produces mechanical effects which 

 are externally perceptible, besides these, heat must also 

 proceed from every muscular action. This proposition, 

 which we here bring forward as a conclusion from the 

 most universal lessons of the action of powers, has 

 already long been acknowledged as a principle derived 

 from experience. 



It was by no means easy to prove this proposition. To 

 be sure, it is rendered extremely probable by the daily ex- 

 perience, that our bodies are perceptibly heated by great 

 muscular exertion, and give off more heat than during 

 the same time with the muscles at rest. But this does 

 not afford an accurate proof. It might be represented 

 that the excessive activity of the muscles only afforded 

 increased opportunity for heat-producing combustion in 

 other constituent parts of the body, for instance in 

 the blood. .An exact proof can, therefore, only be given 

 by putting in action a muscle severed from connection 

 with the rest of the body, and proving that heat is de- 

 veloped therein. Such experiments can, of course, only 

 be made on the muscles of cold-blooded animals, because 

 those of the warm-blooded, when separated from the 

 body, lose their vital properties too quickly. 



The first person who made such experiments and has 

 shown an increase of temperature, that is a development 

 of heat in isolated muscles by action, was Helmholtz. 

 This fundamental fact could not fail to attract great at- 

 tention, and make people endeavor to ascertain what cir- 

 cumstances had an influence on the greater or less de- 

 velopment of heat by muscular action. The most im- 

 portant labors in this direction proceeded from Heiden- 

 hairis laboratory. He has especially much improved the 

 thermo-electric system, which alone can be used to as- 

 certain the increase of temperature of the muscles. With 

 the aid of this system one can distinctly perceive even the 

 extraordinarily slight increase of temperature, which a 

 little frog muscle undergoes at a single, by no means en- 

 ergetic, movement, that scarcely amounts to r hu of a 

 Centigrade. In successive experiments it can even be 

 determined, in which mote, and in which less, heat was 

 developed, but until now the system has not been 

 thoroughly adapted to fix the absolute value of the in- 

 crease of temperature. 



Some time ago I succeeded in so changing the thermo- 

 electric apparatus, that it is possible, by its means, to fix 

 with some degree of accuracy, the increase of tempera- 

 ture a muscle experiences in its action. Thereby the 

 possibility was instantly afforded, of stating in the usual 

 units the quantity of heat developed by the muscular ac- 

 tion. This quantity of heat is namely, evidently, the in- 

 crease of temperature multiplied by the capacity for heat 

 of the proportion of muscle used, which latter is assumed 

 to be about equal to -, 2 - of the capacity for heat of a body 

 of water of equal size. 



According to a general observation previously made, 

 the whole labor performed in the muscular act by chemi- 



cal powers of attraction can now be definitely deter- 

 mined. For this purpose it is only necessary to allow the 

 muscular action to pass away, so that finally no sort of 

 mechanical effect remains; then, since every labor of 

 forces must leave an effect, a quota of heat will exist that 

 will be the exact equivalent of the work performed by the 

 chemical powers. The condition just expressed may be 

 fulfilled by simply letting the muscle, in its action, raise a 

 weight; but allowing this to fall again, so that it pulls 

 the muscle which meantime has relapsed into a state of 

 rest. In so doing the work performed by the weight of 

 the falling body will evidently be used for the develop- 

 ment of heat in the apparatus. To be sure, it might now 

 be asked, in what portions of the whole machinery used, 

 this amount of heat is developed. Theoretically it is be- 

 yond doubt, that a portion of it is set free in the interme- 

 diate pieces, which connect the weight with the muscle, 

 especially by the friction at the points of union, but since 

 these intermediate pieces are practically non-ductile, and 

 the friction at their points of union can only be very 

 slight, it may be assumed from the beginning, that the 

 quota of heat in question is almost entirely released in the 

 body of the muscle itself, which, by its extreme ductility, 

 receives, so to speak, almost entirely the shock of the fall- 

 ing burden. This supposition is so probable, that in the 

 exact scientific publication of the result of my experi- 

 ments, I have pre-supposed it as a matter of course. 

 Meantime I have made experiments in my laboratory, 

 which render this supposition one empirically shown. 



The experiments have been made in the following man- 

 ner. A body of known weight fastened to the muscle 

 was raised, not by its own action, but by other labor to a 

 measured height and then allowed to fall. The increase 

 of temperature experienced by the muscle inconsequence 

 of the jerk was now measured, and by multiplication with 

 the capacity for heat of the muscle, the quantity of heat 

 developed in the muscle was ascertained. It usually cor- 

 responded in a really surprising manner with the thermic 

 equivalent of the mechanical labor, which was applied to 

 raise the appended burden. This affords the proof, that 

 the heat produced by such a jerk is liberated almost en- 

 tirely in the muscle, and only very inconsiderable fractions 

 are developed in the other portions of the machinery used. 

 Every such experiment can thus be looked upon as fixing 

 the mechanical equivalent of heat, which, of course, in 

 point of accuracy, falls far behind the purely physical 

 tests, but is worthy of notice because a living tissue is 

 the means of ascertaining it. To us, however, the in- 

 terest of these experiments consists in the fact that they 

 prove the reliability of the system used to fix the heat of 

 the muscles. 



Let us now return to the development of heat by ac- 

 tive muscular action, and consider more closely the nu- 

 merical product of an accurate experiment. That in the 

 estimates of the quantities of heat, and afterwards the 

 value of labor too, many ciphers may not appear imme- 

 diately behind the comma, we will base them upon units 

 a million times smaller. So, for the unit of heat, we will 

 take the quantity of heat necessaiy to raise the tempera- 

 ture of 1 mgr. of water from o° to 1°. As the unit of 

 labor we will choose instead of the kildgrammeter the 

 grammillimeter. The equivalent proportion, therefore, 

 remains unchanged — 425. For an experiment a body of 

 muscle weighing 31 14 mgr. had lifted in ten pulls, rapid- 

 ly succeeding each other, a burden of 500 gr. 10 times, 

 and the latter had fallen again as many times, so that at 

 last it hung no higher than at first. The temperature of 

 the mass of muscle was increased 0,0195° by this act. 

 Now, since 31 14 mgr. of muscular substance possesses 

 exactly as much capacity for heat as 2803 mgr. of water, 

 the increase of temperature which followed, required 

 2803X0,0195=54, 6 units of heat. But in our experiment 

 the production of this quantity of heat is the only effect 

 of the work accomplished by the chemical powers of at- 

 traction in the muscular action. It must, therefore, ex- 



