CHAPTEE I 



ORGANISATION AND STRUCTURE OF MUSCLE 



EVEN at a low grade of differentiation there is a wide range of 

 Fibrillated Structures in contractile protoplasm, and the great 

 significance of this organisation for the contractile process and 

 motor phenomena of protoplasmic substance is unmistakably 

 attested by the behaviour of ciliated cells, and of spermatozoa in 

 particular. 



Without entirely subscribing to the theory recently brought 

 forward by Ballowitz (1) and others, " that all regular, definitely 

 canalised contractions of contractile substances denote the presence 

 of regular, parallel, or approximately parallel fibres " (against 

 which there is much counter-evidence), it is nevertheless remark- 

 able that a fibrillated structure of protoplasm is more or less un- 

 equivocally present in nearly every case of energetic, and especially 

 of rapid, contraction. This is expressed most clearly in the 

 highest differentiated forms of contractile animal protoplasm, i.e. 

 Muscle -fibrils, Muscle-cells, and Muscle-fibres. 



It appears to be of fundamental importance, as well morpho- 

 logically as physiologically, to the conception of " muscle " that 

 structures which, in virtue of organisation and function, may 

 properly be termed muscular, first appear as single and isolated, 

 or fasciculated, fibrils. This is as true of ontogenetic as of phylo- 

 genetic development. On examining the latter, we encounter the 

 first genuine muscles in some of the ciliated Infusoria, for it is at 

 least doubtful whether the delicate and swiftly contracting proto- 

 plasmic threads of certain fresh- water Heliozoa (AcantJwcystiden), 

 which Engelmann (2) calls " myopodia," or the analogous structure 

 of many Eadiolaria, the " myophrysken " of Haeckel, are true 

 muscle-fibrils. In either case we may assume, with Engelmann, 



