122 MUSCULAR TISSUE. 



Kiihne names myosin, is liquid ; but if it be then exposed to the ordi- 

 nary heat of the atmosphere it partially coagulates, and the portion 

 then remaining liquid (the muscle-serum) when heated to 112° R, or 

 less if it be strongly acid, yields a further coagulum, which Kidme con- 

 siders peculiar to muscle ,- and finally, at 1G7°, ordinary coagulated 

 albumin. The primary coagulation is hastened by the presence of 

 blood, and possibly it may be due to the mutual reaction of two albu- 

 minoids analogous in their operation to the fibrinogen and para-globulin 

 of the blood (ante, p. 29). The coagulum of myosin is soluble in 

 strong solutions of neutral salts, and accordingly it may thereby be 

 dissolved out of dead and rigid muscles ; but it loses this property if 

 previously dissolved in dilute hydrochloric acid. It then, in fact, 

 agrees with the so-called syntonin, which Kill me regards, not as an 

 original albuminoid of muscle, but as myosin altered by the process of 

 extraction. It has been suggested that the ready solution of muscular 

 fibre in dilute hydrochloric acid may be owing to the presence of 

 pepsin in minute quantity. 



Other substances also exist in muscle, but in very small propor- 

 tion in comparison with the albuminoid matter. Most of them 

 probably result from the process of wear of the original muscular 

 ■substance. Amongst them are, — 1. Ivreatin and kreatinine, both 

 of them nitrogenized and crystalline, the former neutral, the latter 

 (derived from it) alkaline ; both are also found in the urine. 2. Sarkin. 

 3. A substance termed " carnin," hitherto only found in Liebig's ex- 

 tract of beef (Weidel). 4. Non-nitrogenized substances, viz. : grape 

 sugar; inosit — an unfermentable sugar from the tissue of the heart; 

 glycogen, at least in embryos and young animals. 5. Various organic 

 acids, viz., lactic, inosinic, butyric, acetic, formic, and uric. 6. Salts, 

 in which potash predominates over soda, magnesia over lime, and phos- 

 phoric acid over chlorine, — muscle, in this respect, resembling blood- 

 corpuscles as contrasted with serum. Lastly, a variable amount of fat 

 may be extracted from muscle, and also gelatin; the latter no doubt 

 from connective tissue ; for it must be remembered that a piece of 

 muscle subjected to analysis comprehends, along with the proper mus- 

 cular fibres, more or less of connective tissue, blood-vessels and nerves. 

 The account here given of the chemical constitution of muscle applies 

 especially to the striped variety, but, so ftir as is known, it is essentially 

 the same in the non-striated tissue, and recent researches point to the 

 probability that ordinary protoplasm possesses a similar chemical 

 constitution. 



The juice expressed from a muscle after death, and especiallj- after rigidity has 

 set in. is acid, from the presence of lactic acid : so that the cut surface of a dead 

 muscle reddens litmus-paper. On the other hand, a perfectly fresh section of 

 muscle in the living bodj'. or while it retains its irritability, is alkaline or neutral. 

 But, while this is true of a living muscle in its usual state, it gives a decided 

 acid reaction after it has been strongly exerted, as. for instance, after tetanic 

 spasm excited by electricity or by strychnia poisoning. The acid is probably 

 generated by a change in the saccharine matter of the muscle. Ultimately 

 the tissue in all cases becomes alkaline from putrefaction and the evolution of 

 ammonia. 



Physical properties of muscle. — A dead muscle has little strength, and may 

 be torn asunder l)y a force of no great amount. A living muscle readily yields to 

 extension, and shrinks exactly- to its original length when the extending force 



