ENERGY AND RAPIDITY OF MUSCULAR CONTRACTION. 839 



an instance of a man, who could raise a weight of 300 Ibs., by the action of 

 the elevator muscles of his jaw ; and that of a slender girl, affected with 

 tetanic spasms, in whom the extensor muscles of the back, in the state of 

 tonic contraction or opisthotonos, resisted a weight of 800 Ibs. laid on the 

 abdomen with the absurd intention of straightening the body. 



688. Absolute Force of Muscle. The mechanical power-exerted by muscle 

 in contraction may be calculated as in any mechanical machine by multi- 

 plying the weight lifted by the height to which it is raised. Weber obtained 

 the following values for the muscle of a frog : 



Weight lifted in Mechanical effect in 



Grammes. Height in Mm. Grammilliiuetres. 



f '27.6 1 f 138 



X bv \ 25 l 376 



11.45 ] 286 



[ G 3 J L i!20 



That is to say, that 138 grammillimetres are equal to 5 grammes raised 

 27.6 mm. or to 27.6 grammes raised 5 mrn. It will be seen from the table 

 that the mechanical effect increases to a certain point with the weighting, 

 and then gradually diminishes : it was found that different muscles had their 

 maximum at different weightings. The power of the muscles appears to 

 vary in different animals, being greatest in proportion to their size in In- 

 sects. 1 The relation of the muscles of the same animal to one another is 

 very simple, the weight which can be raised, as Professor Haughtou 2 states, 

 being proportional to the area of the cross section of each muscle, and may 

 even be estimated by the cross section of the tendon that conveys its influ- 

 ence to a distant point; whilst it is obvious that a given weight can be raised 

 higher in proportion to the length of the muscle. The most natural measure 

 of the maximum of force which is exerted when the muscle is in its highest 

 state of excitability is the amount of work it can accomplish under the in- 

 fluence of the strongest stimulus. But this, as is shown above, is found to 

 vary with the degree of weighting ; and it is, therefore, advantageous to 

 adopt another measure to which the term "absolute muscle-force" may be 

 applied. 3 This is represented by the weight, which is exactly equivalent to 

 the contractile power of the muscle when stimulated to its utmost, or, in other 

 words, which the muscle, when most strongly stimulated, is just incapable of 

 raising. The absolute muscle-force for the square centimetre of the muscles 

 of the frog was estimated by Weber at 692 grammes. Koseuthal 4 gives a 

 higher number for the muscles of the same animal, estimating it at from 

 2300 to 3000 grammes per square centimetre of cross section for the adductor 

 magnus and semi-membrauosus, and from 1000 to 1200 grammes for the 

 gastrocnemius ; whilst for the square centimetre of the muscles of man 

 Henke and Knorz have estimated it at from 60,00 to 8000 grammes; and 

 Koster 5 at about 10,000 grammes per square centimetre for the muscles of 

 the leg, and 7400 for those of the arm. Haughton's estimate 6 agrees very 

 closely with those of Heuke and Knorz, since he considers the absolute 

 muscle-force of the muscles of the human arm to be 94.7 Ibs., of the leg to 

 be 110.4 Ibs., and of the abdomen to be 107 Ibs. for the square inch of sec- 

 tional area, which reduced to French measure 7 would amount to about 



1 See Plateau, Revue Suisse, t. xxv, 1866, p. 87, who states that the Donacia nym- 

 phsea can overcome a resistance equal to 42 times its own weight. 



2 Proceedings of Royal Society, 1867, No. 94. 



3 See Hermann, Grundriss der Physiologic, 1867, p. 238. 



4 Comptes Rcndus, torn. Ixiv, p. 1143. 6 Archief Nederland, Bd. ii, No. 2. 



6 Proceedings of the Royal Society, 1867, No. 94. 



7 Taking the square inch at 6.45 square centimetres and the pound avoirdupois at 

 453 59 grammes. 



