Notes on certain physical and physiological measurements and estimates / by John G. M'Kendrick.

  • McKendrick, John G. (John Gray), 1841-1926.
Date:
[between 1800 and 1899]
Catalogue details

Licence: Public Domain Mark

Credit: Notes on certain physical and physiological measurements and estimates / by John G. M'Kendrick. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    8/61 (page 188)
    in the pointing ont of certain striking resemblances between the properties of muscle and those of stretched violin-strings and other lifeless bodies of a similar nature. Fick1 has criticised the hypothesis, pointing out that the absolute force of the muscle is so much greater than that of any such system as Engelmann’s muscle model, that the bounds of legitimate analogy are overstepped. Engelmann professes to have refuted this objection by pointing out the following facts, and making certain deductions from them : (a) that a violin- string ’7 mm. in diameter will perceptibly raise a load of 1 kilo, when its temperature is rapidly raised to 130° C.; (6) that the maximum load that a tetanised strip of human muscle 1 sq. cm. in transverse section can raise is 10 kilo ; (c) that in tetanus a muscle may rise 1° in temperature. From these figures he con- cludes that the string exerts twenty times as much force as the muscle of the same cross-section. But this conclusion cannot fairly be drawn from the figures. For let us assume that the string was raised only 100° C. in temperature. The area of its cross-section is nearly -5 sq. mm. Then the string -5 sq. mm. in cross-section raised 100° C. in temperature lifts 1 kilo. Engel- mann supposes that parts of the muscle are directly heated while others are not, and the rise of the temperature which would give au efficiency of 30 per cent, (which is that of muscle)2 * is 100° C. Then let us suppose the temperature distributed in this most favourable manuer, and we have for the muscle the figures T(\p- sq. cm. raised 100° C. in temperature lifts 10 kilos, i.e., the muscle exerts five times as much force as the string for equal cross-sections. There are two considerations which show that the data of this calculation, as given by Engelmann, are far too favourable for the string. In the first place, he has neglected the question of absolute force ; and probably the muscle raises the weight to a height which is a much greater proportion of its own length than does the string. Secondly, the tetanus during which a muscle rises 1° C. in temperature is one continued for some minutes (cf. L, s. 158). Becquerel observed a rise of temperature of 1° C. after five minutes’ tetamsation, and (s. lot)) Helmholtz observed a rise of temperature of -18° C. on tetams- 2 r.M sSei66^7'[I.’ here and hereafter to Hermann’s Haruibuch d. Phys., ed. 1. ' II. rei'eis to Biedermann’s Elcclro-Physiologie, Bug. tians.]