382 MUSCULAR ACTION 



blood-vessels being large and numerous and intimately distributed, and 

 the nerves of large size and much complexity of course and endings. 

 Lymphatics are abundant in the connective-tissue coverings of the 

 different muscular parts, but do not, anymore than do the blood-vessels, 

 extend into the cells, apparently. (For the nerve-endings of muscle, see 

 the preceding chapter, page 329.) 



CARDIAC MUSCLE is striated in both directions, but always less dis- 

 tinctly than is cross-striated muscle. Another leading characteristic is 

 the relatively large amount of sarcoplasm, as may be seen in Figs. 237 

 and 238, by MacCallum. Moreover, the morphological units (cells) are 

 closely connected in such a way as to appear branched, combining in 

 this way to constitute a coarse striated network made up of sarcostyles, 

 which in turn are strings of sarcomeres. No thick sarcolemma, it is said 

 by some observers, appears, but the sarcostyles have sheaths. There 

 may be three or four nuclei in each cell ; they are oval in shape with 

 distinct chromatin reticulum and surrounded (as in skeletal muscle) with 

 granular protoplasm whose granules increase with the individual's age. 

 Ultimate fibrils compose the sarcostyles as in other sorts of muscle and 

 pass uninterruptedly from one morphological cell to the next. 



The importance of an extension of our knowledge of cardiac muscle 

 for therapeutic reasons cannot easily be over-estimated, the saving of 

 many lives lying in this direction of reasearch. 



The Chemistry of Muscle. This subject is of importance because the 

 muscles, by their metabolism, furnish a large part of the energy and of 

 the heat of the body, and, furthermore, because it underlies the mode of 

 working of the muscle. 



In crude and general terms human muscle is: water, 73 per cent.; 

 proteids, 19 per cent., fats, 2 per cent.; "inorganic" salts, 2 per cent.; 

 and chemical sundries, 4 per cent., these latter being mostly carbohy- 

 drates, purin bodies, and gelatin. It is not obvious that the water of 

 the muscle is concerned in the actual metabolism of the tissue, but, as 

 we have already pointed out, it is essential to the active movement of 

 these, as of all other organs. The proteids of dead muscle may not be 

 those of living muscle, but of the former we know only a little, and of the 

 latter nothing. There are two proteids probably peculiar to muscle: 

 the globulin, called para-myosinogen (called myosin by Furth), and 

 myosinogen. These two proteids become myosin under many condi- 

 tions, this process being probably, for example, at the basis of rigor, 

 mortis. Dubois suggests an instructive formula by which the katabolism 

 of albumin might conceivably be conducted, and it is reproduced here 

 chiefly as a sort of chemical diagram, infinitely simpler, of course, than 

 the reality, and useful chiefly as a list of the products named. 



C 72 H 112 N 18 SO 22 , albumin + 20(H 2 O), water - 



7(CON 2 H 4 ), urea 

 + 5(C B H 10 O 5 ), glycogen 

 + C 27 H 46 O, cholesterin 

 + 3(C 2 H 5 NO 2 ), glycocoll 

 + C 2 H 7 NSO 3 , taurin 

 + 6H, hydrogen 



