VTi STRIATED MUSCLE 289 



connection which the cement substance affords there is 

 clearly some fundamental connection by which the heat is 

 conducted from tibie to fibre. 



4. The Structure of Striated Muscle,— Striated 

 mu^le is also made up of fibres, though the fibres are 

 very different from the fibres or fibre-cells of unstriated 

 muscle, and these fibres are again similarly bound up 

 together in various ways, by connective tissue which 

 carries the blood-vessels and nerves, so as to form 

 muscles of various shapes and sizes.' Each muscle 

 is thus made up of (i) an external wrapping or peri- 

 mysium ; this is a sheath of connective tissue from 

 the inner face of which partitions proceed and divide 

 the space which it incloses into a great number 

 of longitudinally disposed compartments ; (ii) the mus- 

 cular fibres which occupy these compartments ; (iii) 

 the vessels which lie in the sheath and in the 

 partitions between the compartments, and thus sur- 

 round the muscular fibres without entering them ; (iv) 

 the motor nerves which also at first lie in the sheath 

 and in the partitions between the compartments, but 

 which eventually enter into the muscular fibres. 



The penmysimn forms a complete envelope around 

 the muscle, which, when it is sufficiently strong to be 

 dissected off, is known as a fascia ; at each end it 

 usually terminates in dense connective tissue (tendon), 

 w^hich becomes continuous with the bone or cartilage to 

 which the tendon is attached. The partitions given off 

 from the inner surface of the perimysium form at first 

 coarse compartments, inclosing large bundles, each con- 

 sisting of a very great number of fibres. These large 

 bundles are again divided by somewhat finer connective 

 tissue partitions into smaller bundles, and these again 

 into still smaller ones, and so on, the smallest bundles of 



1 It is necessary to distinguish "muscle" as an organ from "muscle ' 

 as a tissue. The biceps miiscle (p. 306), for example, is an organ of a 

 complicated character, of which muscular tissue forms only the chief 

 constituent. 



U 



