THEIR HISTOLOGICAL RELATIONS. 75 



between the sarcolemma of the different bundles we find the 

 well-known vascular network of the muscles, with its gene- 

 rally rectangular meshes, and the tortuous windings of the nerves. 

 It is not a settled point whether the sarcolemma in the developed 

 muscle contains nuclei ; that is to say, whether the nuclei, which 

 are apparently perceptible in it, appertain to it, or whether they lie 

 under it, and belong to the muscular fibrils of the primitive bundles, 

 and therefore to the contents of the sheaths of sarcolemma ; at all 

 events, we may perceive in the sarcolemma roundish nuclei, fre- 

 quently resembling drops of oil, or, more rarely, having a spindle- 

 like form, of which some at all events, according to Schwann and 

 Kolliker, are situated between the sarcolemma and the muscular 

 fibrils, but are not intimately connected with any of these parts. 

 We find, as has been already observed, that the substance inclosed 

 in the sarcolemma always presents a strongly marked transverse 

 striation, and generally a less distinct longitudinal marking ; so 

 that the primitive bundles might just as readily be supposed to 

 consist of superimposed discs (Bowman) as of long, transversely 

 striated fibrils. In muscles, however, which have been submitted 

 to chemical treatment (whether simple boiling or the action of 

 reagents), we very frequently see a separation or disintegration 

 of the contents of the sarcolemma into constricted filaments, which 

 has led most histologists to regard these contents as composed of 

 fibrils. It is very generally believed that the constrictions of the 

 transversely striated primitive fibrils stand in the closest relation 

 to the function of the muscles ; on making a microscopical exami- 

 nation of the muscles of just killed or still living caterpillars, we 

 perceive the dark stripes approach one another, and again separate. 

 In paralysed muscles (which have not yet undergone fatty degene- 

 ration) these stripes are observed to be more widely separated from 

 one another than in healthy muscles, &c. 



Although several very admirable investigators will not admit 

 that these observations afford sufficient evidence of the essential 

 part which these constrictions of the elementary fibrils take in 

 muscular contraction, the constrictions, or, perhaps, more cor- 

 rectly speaking, varicose dilatations, which are so constantly observed 

 in this group of animal fibres, cannot be wholly purposeless or 

 accidental ; for, granting that our theory of the contraction of the 

 fibrils is very complicated, the want of homogeneity in the fibres 

 must exert some influence on their contraction. The elementary 

 fibres are assuredly not formed of an entirely homogeneous sub- 

 stance ; for, in the first place, we occasionally see the muscular fibre 



