86 TRANSVERSELY STRIPED MUSCULAR FIBRES. 



tissue is certainly coloured yellow by nitric acid (especially on the 

 addition of potash), and this is also the case in the empty sheaths 

 which remain after the repeated treatment of muscular fibre with 

 a dilute solution of soda, and a thorough rinsing with water ; but 

 we are yet without any conclusive proof that these tissues were 

 wholly free from all protein-like substances when they were 

 submitted to the action of the nitric acid, and it would be ex- 

 tremely difficult to prove that such was the case. 



We have already frequently referred to Liebig's admirable 

 investigation of the fluids contained in the flesh ; these researches 

 have not only tended materially to elucidate a very obscure sub- 

 ject of inquiry, but have also thrown considerable light on nearly 

 all departments of physiological chemistry. We have now merely 

 to consider generally the composition of the juice extracted from 

 the striped muscles, and to enlarge somewhat more fully upon 

 certain points of discussion which had before been only incidentally 

 touched upon. 



The freshly expressed muscular juice is generally of a whitish 

 colour, and turbid or opalescent from the presence of suspended 

 fat ; it reddens litmus paper very strongly, and forms on boiling a 

 considerable coagulum ; acetic acid, moreover, gives rise to a 

 turbidity, which depends upon the presence of casein in the fluid, 

 as I have satisfied myself by the application of rennet, &c. As 

 the true muscular juice cannot of course be obtained without the 

 admixture of the transudation entering into the connective tissue, 

 and of the blood contained in the vessels of the muscular sub- 

 stance, a very great part of the albumen may be derived from this 

 source ; but the amount present is too large to be referrible to this 

 only, more especially as we have met with it in considerable 

 abundance in comparatively non-vascular tissues provided with 

 smooth muscles, as, for instance, in the middle coat of the arteries. 

 The casein must, however, be derived solely from the true mus- 

 cular juice, since, as we have already shown in vol. i, p. 381, its 

 presence cannot be demonstrated with certainty in the blood. We 

 have already spoken at length, in vol. i, pp. 136, 141, 222, and 98, 

 of the occurrence of creatine, creatinine, inosic acid, and lactic acid, 

 in the muscular juice. 



Scherer* has discovered a special substance in the decoction of 

 the flesh of the heart of the ox, to which he has applied the term 

 inosite. [See note to vol. i, p. 281 (on inosite) in the Appendix. 

 G. E. D.] 



* Ann. d. Ch. u. Pharm. Bd. 73, S. 328-334. 



