6i8 



SCIENCE. 



THE DEVELOPMENT OF HEAT BY MUSCULAR 

 ACTIVITY. 



By Professor A. Fick, of Wurzburg. 



It is the object of physical science in the proper sense 

 of the word, to perceive in all the phenomena, of nature 

 the operations of the same forces, with which any two 

 material particles always act upon each other, when they 

 come in contact with each other in the same relations. 

 This object has never been so clearly seen by the majori- 

 ty of naturalists, as during the last decade. Since that 

 time a lavv already proved in mechanics has been recog- 

 nized as one applicable to all the events of nature. It is 

 called by Helmholtz, who in a treatise which appeared 

 thirty-one years ago, first demonstrated its universal im- 

 portance, the " law of the preservation of power" ; re- 

 cently the designation " law of the preservation of energy" 

 has also been brought into use by English men of science. 

 The amazing productiveness of this iundamental law of 

 the operation of all natural forces essentially consists in 

 the fact that from it may easily be derived experiments 

 for testing results even in natural phenomena, in which 

 in detail the nature of the acting forces is wholly con- 

 cealed. 



Therefore it could not fail to happen, that since this 

 time individual investigations in the most varied depart- 

 ments of physical science have principally turned upon 

 this fundamental principle. It now seems to me that the 

 results of such individual investigations, which are con- 

 nected with the mojt universal points of view, might be 

 best adapted to secure interest even outside the circle of 

 the scientists. In this opinion I will venture to claim the 

 attention of the readers of this publication for some 

 general observations connected with an experiment made 

 by me a short time ago, and elsewhere communicated to 

 persons familiar with such matters. 



Each individual can experience in his own body at any 

 moment, that with the aid of his muscles he can conquer 

 opposing forces and set masses in motion. The former 

 happens, for instance, when we lift a burden or throw 

 the whole weight of the person upward in climbing a 

 mountain ; the latter occurs when we hurl a stone or 

 swing a hammer. The principle of the preservation of 

 power now demands that, where we see forces conquered 

 or masses moved, necessarily powers on the other side 

 have '"acted" or performed labor, that is, that the points 

 of assault of forces have been displaced. This, for in- 

 stance, is clearly apparent in the voluntary fall of a heavy 

 bodv. It is the point of attack of a power directed down- 

 ward, namely weight, and as under the influence of this 

 power it moves downward, its velocity increases ; or when 

 in a wavering balance one scale with its burden ascends — 

 its weight is conquered — but the other sinks and its weight 

 performs a certain amount of work. So if by the medi- 

 ation of muscular action we see forces conquered or 

 masses moved, it must be asked : what powers have 

 acted or performed the labor here, that is, have changed 

 their points of attack in their action. 



Forces which, for instance, like weight, act upon 

 larger bodies in a similar manner, will not of course be 

 alluded to here. The point in question can only concern 

 powers that operate even among the smallest particles of 

 muscular substance, that is chemical powers of attrac- 

 tion. Something must take place in the muscle similar 

 to what occurs in the steam-engine, when in the act of 

 combustion under the boiler the particles of carbon and 

 oxygen, obeying their strong reciprocal power of attrac- 

 tion, rush towards eich other, makng violent little move- 

 ments, and a portion of this energy, by means of a series 

 of shocks, is applied to the conquest of opposing forces, 

 or to accelerating the speed of bodies. So in the muscle, 

 during its activity, chemical processes evidently take 

 place, with which powerful kindred forces come into ac- 

 tion. That this is really the case can be shown by ex- 

 periments. Singularly enough, it is not only an analog- 



ous, but for the most part at any rate precisely the same 

 chemical power of attraction which performs the work 

 in the active muscle and in the steam-engine, namely the 

 power of attraction between the particles of carbon and 

 the particles of oxygen. The product of the operation of 

 this power of attraction, carbonic acid, appears in a cer- 

 tain quantity at every act of muscular motion. 



In all the examples, in which, by the mediation of any 

 arrangements, through whose operation the action of 

 chemical powers of attraction, taking place even in ex- 

 traordinarily small distances, accelerates the movement of 

 bodies, or overcomes mechanical forces, like weight, a 

 general remark may be made, which has hitherto been 

 everywhere confirmed by experience. The lines of com- 

 munication between the particles undergoing a change 

 by means of a chemical process are usually irregularly 

 distributed in every part of the space. The movements 

 arising from the individual processes of change are, there- 

 fore, also irregularly driven in all directions, and thus can 

 Dever be applied in their full strength to overcome an 

 opposing force acting in a fixed direction, or to accelerate 

 the speed of a body, whose particles are all moving in the 

 same direction. Only a portion of this collected energy of 

 motion can appear in such a form. A fraction, greater or 

 less, according to circumstances, of the sum of the indi- 

 vidual processes of change must retain its original form 

 of the irregularly whirling movement of the tiniest par- 

 ticles. This conclusion may, therefore, be briefly ex- 

 pressed thus : wherever in a chemical process the power 

 of attraction of the smallest particles of different sub- 

 stances performs labor — no matter under what circum- 

 stances this may occur — a portion of the labor will al- 

 wavs be employed in the development of heat. 



The heat contained in a body is, therefore, nothing else 

 than the energy of slight invisible irregular whirling 

 movements, in which the tiniest particles of the body are 

 included. To increase the temperature of a body, there- 

 fore, is merely to increase the energy of these irregular 

 molecular movements of the smallest portions. This 

 view instantly finds support in the common phenomenon, 

 that at the increase of the temperature of a body above a 

 certain degree its particles in consequence of the colossal 

 energy of motion really pulverize each other — " the body 

 evaporates." 



If this view of heat is correct, a certain degree of heat 

 can be produced by a certain amount of work. The propor- 

 tion of work, or the operation of a power is, as is well 

 known, the product of the intensity of the power and the 

 distance through which it has acted. Therefore the pro- 

 duct of the unit of the intensity of the power, the kilogram, 

 and the unit of the distance, the meter, is chosen as the 

 unit of this power. This unit of the value of the work 

 is called the kilogrammeter. As the unit of the quantity 

 of heat the same degree has been fixed that is required 

 to be supplied to a kilogram of water, when its temper- 

 ature is to be raised from o° to i° of the Centigrade. 



Natural philosophy has now succeeded — and it is one 

 of its most important achievements— in showing, that for 

 the production of a unit of heat an expenditure of work 

 of 425 kilogrammeters is requisite. This number is called 

 the m chanieal equivalent of heat, because it is thereby 

 possible to calculate each quantity of heat in a certain 

 number of mechanical units of work, which is requisite 

 for its production. 



The knowledge of the mechanical equivalent of heat 

 enables us to measure exactly the work performed by any 

 chemical process of kindred forces operating even at 

 immeasurablv little distances, although we know nothing 

 at all of the laws of action of these forces in detail. In 

 fact, we need only direct the process, so that no effect is 

 produced except the development of heat. If we then 

 measure the heat developed and multiply the number of 

 units found by 425, we shall have the labor which the 

 chemical powers of attraction have performed in the pro- 

 cess, expressed in kilogrammeters, since according to the 



