Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee.

  • Gamgee Arthur, 1841-1909.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    energy; the position of its weiglits or of its spring cannot then be converted into motion. So soon, however, as the catch is withdrawn, the potential energy- becomes kinetic, the weight falls or the spring approaches its original form, and the clock goes. The force which removes the catch, which therefore liberates the clock, and liberates its potential energy, may be called ' the liberating force.' Its magnitude often bears no proportion to that of the energy set free; the same force which withdraws the catch which impeded the motion of a clock driven by a gramme weight, might also liberate a clock driven by a hundred weight. Other examples of such liberations are:— A spark which inflames a mass of gunpowder, and consequently sets free enormous quantities of energy, or a slight movement which closes the circuit of a powerful battery. There occur, however, cases of liberation in which the liberating force does not, as in the cases cited above, instantly set free the whole store of energy, but only a portion, which bears a definite, though it may be a complicated, relation to its own magnitude. Let us take the case of a head of water confined by a sluice with a rectangular door. The quantity of water which will flow out, and the kinetic energy represented by its fall, will depend upon the height to which the sluice-door has been raised, and upon the force—here acting as a liberating force—expended in raising it. All the phenomena of liberation which occm* in the body appear to bear some resemblance to the last case which has been cited. A closer survey of the nervous system reveals the fact that not only does it exert a liberating influence on the organs of xvork of the body, but that its own constituent parts exert a similar action one upon the other. By organs of work we may shortly designate those organs, such as muscles and glands, in which con- siderable amounts of energy become kinetic and apparent to us in the form of mechanical work, heat, &c. A portion of the nervous system—that engaged in conducting —may be looked upon as consisting of series of elementary parts, of which each one possesses a certain amount of potential energy, and which are so closely connected together that the energy which has been liberated in one part serves to liberate the energy of the adjoining elementary parts; thus, a liberating force which acts on the first of these elementary parts produces a series of liberations, until at last the energy set free in the ultimate particles situated in some other organ (as an organ of work) brings about the libera- tion of _ forces within that organ. We distinguish two kinds of liberating-chains, possessing distinct origins and terminations. The one kind proceeds from the so-called organs of the senses, i.e. from organs on which an external influence (as pressure, heat, sound, light, &c.) acts as a liberating agent, and terminates in the so-called central organs of the nervous system; to which we give the name of centripetal chains, or centripetal nerveS; The second kind (the centrifugal chains), on the other hand, proceeds from the central organs of the nervous system, and terminates in the organs of work. The central organs of the nervous system may, consequently, be looked upon as the points of departure and of entrance of bberating-chains. We are, however, unacquainted with the natiu-e