94 



APPAEATTTS OF MOTION. 



the fasciculi into fibres, we can readily understand one feature 

 of voluntary muscle the tendency which it shews to separate 

 in the longitudinal direction by a kind of natural cleveage. 

 The following figures from Wagner illustrate most clearly the 

 different forms of muscular tissue. T.W.] 



In Fig. 60 we have a fresh muscular fasci- 

 culus of the ox, one-thirtieth of a line in thick- 

 ness. The upper extremity of the bundle 

 exhibits transverse striae only ; but they ap- 

 pear to fail here and there, and these gaps 

 seem as if they separated fibrils or bundles of 

 fibres at some little distance from one ano- 

 ther ; the opposite or lower end of the fasci- 

 culus, on the contrary, shows nothing but 

 longitudinal striae or primitive fibrils, an effect 

 which is entirely due to the focussing of the 

 microscope. At the place where the muscular 

 bundle is torn through (inferiorly ) a scaleform 

 appearanceis perceived very beautifully brought 

 out by the different layers of the primitive fibrils, 

 which have contracted again in different de- 

 grees after yielding to the tearing force ; in 

 the middle of the specimen the microscope is 

 so focussed that transverse and longitudinal 

 striae are perceived at the same time; here 

 the former, there the latter, more distinctly, 

 according to the difference of level of the 

 surface of the fibre examined. The trans- 

 verse striae are in a general way extremely 

 constant, and a highly characteristic indi- 

 cation of the muscular fibre of animal life, so 

 that the smallest portion of a muscle belong- 

 ing to this system is at once recognized under 

 the microscope by their presence. The trans- 

 verse striae, however, become extremely faint 

 under many circumstances ; in bodies with 

 very soft or flabby muscles, and in very young 

 animals, for example ; but even here they are often very distinct, and are 

 readily studied in the living larva of the frog, near to the spinal column 

 in the' tail. They are very distinct in boiled and roasted meat, and in 

 muscle that has been macerated inspirit (Fig. 61, 62, B), in which, indeed, 

 they often present themselves as absolute transverse rugae, with lateral 

 notchings, so that we should be very apt to suppose that a peculiar sheath 

 enveloped the muscular bundles, a supposition which gains strength from 

 the fact, that towards the torn ends of the specimen, the primitive fibrils 

 are often seen free, isolated, and without any appearance of cross-barring 

 (Fig. 62, A). On the other hand, however, we frequently recognize the 



