418 GENERAL ANATOMY. 



the primitive fibres. It would seem that before they disappear 

 altogether, they become soft, divesting themselves'of their own 

 jenvelop, so that their medullary substance comes in imme- 

 diate contact with the muscular fibre. Munro and Smith 

 thought they had perceived that the nerves of the muscles 

 have their fibres twisted in a spiral line. 



According to Messrs. Prevost and Dumas,*,the nerves of 

 the muscles are perceived in the following manner in prefer- 

 enc^e to any other: a bit 'of the muscle of beef is examined after 

 being macerated in pure water, and in a dark place; by throw- 

 ing a cone of lively light on the muscle only, we distinguish 

 the colour of the nerve to be obviously different from that of 

 the muscle, and it can be traced very far by means of a good 

 lens, and a very slender scalpel; the ramifications are then seen 

 to terminate by inserting themselves between the muscular 

 fibres, the direction of which they cut at right angles. In or- 

 der to observe this arrangement throughout the whole mass of 

 a muscle thin enough to be transparent/the rectus abdominalis 

 of the frog is laid on a thin plate of glass, it is examined by 

 illuminating it by transmission by means of a weak magnify- 

 ing glass and the light of a candle: the nerve and its twigs are 

 then perceptible, and may be distinguished from the muscula^ 

 fibres and their direction. In fact, the trunk of the nerve con^ 

 tinues its course through the thickness of the muscle parallel 

 to its length, and its branches separate from it at right angles 

 to enter between the fasciculi and the muscular fibres; and as 

 they are all formed on the same plan, because of the moderate 

 thickness of the muscle, they represent a sort of comb. If the 

 muscle be contracted, th'e last visible transverse fibrils of the 

 nerve are seen to correspond exactly with the summit of the 

 angles, or of the flexuosities of the muscle. 



The nerves, though numerous and voluminous in the mus- 

 cles, escape the sight long before their divisions are by any 

 means sufficiently multiplied to admit of their being distributed 

 to all the muscular fibres. Two hypotheses have bee'n imagin- 

 ed to explain their action in all the fibres. Isenflamm and M. 



* Unpublished memoir. 



