452 BIOLOGY. [BOOK vn. 



The muscular temperature in man has especially been deeply 

 studied by M. Becquerel. With thermo-electric needles he has 

 seen the muscular temperature rise 1 degree and some tenths, 

 after violent exercise. At the same time, the venous blood 

 issuing from the muscle, and which, during the period of repose, 

 was moderately black, becomes of an intense black, and its 

 temperature rises. On the contrary, in paralysis by nervous 

 section, when the tonic muscular contraction is itself abolished, 

 the blood issues from the muscle rutilant, and scarcely oxydised. 



The production of heat, during muscular contraction, is then 

 manifestly dependent upon oxydation. It is demonstrated also 

 by compressing the nutritive artery of the muscle, which imme- 

 diately causes a remarkable coldness (Becquerel) ; by paralysing 

 the muscular system of a dog with curare, which lowers the 

 temperature of the animal several degrees in an hour (id.) ; by 

 causing the muscles of a frog confined in a bocal to contract by 

 means of electricity, and by proving that these contractions have 

 caused the production of carbonic acid (Matteucci). 



This last fact proves, besides, that the muscle can contract, 

 oxydise itself, and engender heat, without being traversed by a 

 sanguineous current. The interfibrillary muscular juice, and 

 perhaps the substance itself of the contractile fibre, are for some 

 time sufficient to produce the indispensable chemical reactions. 

 These reactions, which always necessitate a certain absorption of 

 oxygen, have been variously interpreted. It is certain that the 

 resting muscle is alkaline, and that contraction acidifies the 

 muscular juice. The acid is lactic or sarcolactic acid. The 

 alkaline principle is creatinine, which transforms itself into 

 creatine. According to another explanation, the muscular fibre 

 does not wear itself out through labour (Yoit), which is very 

 improbable. There is in the resting muscle an azotised sub- 

 stance, inogen, which, during contraction, evolves into carbonic 

 acid, lactic acid, and an albuminoidal substance, myosine. It is 

 myosine which in solidifying produces rigidity of the muscle. 

 The development of heat, and also the production of mechanical 



