1862.] 75 



truncules as they may be called, each, however, being but a single fine 

 fibre ; one of these (fig. 2 b), larger than the rest, supplied the upper 

 part of the muscle with branches, two (c, d) went to the middle, and 

 two rather long ones (e, f) were distributed on the lower part of the 

 muscle. As to the original source of these truncules, I agree with 

 Reichert in thinking that they are all derived from one principal 

 sentient fibre, which is mixed up with the more numerous motor" 

 fibres in the small nerve , , a, which is supplied to the cutaneous 

 muscle. It is true that I have not been able, any more than 

 Reichert, actually to trace 'back these truncules to their parent 

 fibre in the trunk of the common nerve. Nevertheless I feel much 

 confidence in believing that they arise in the way stated; and 

 especially because I have met with cases in which the parent fibre of 

 all the sentient nerve-fibres of the cutaneous muscle escapes from 

 among the motorial fibres of the common muscular nerve at some 

 distance from the muscle ; so that its division into the secondary 

 truncules may be seen. Moreover I have never seen fibres, which from 

 their final distribution may be reckoned as motory, coming from the 

 sentient fibres, nor the latter from the former; although I have 

 sometimes met with a deceptive appearance to the contrary, caused 

 by true motor fibres attaching themselves for a little way to a 

 sentient fibre, and then seeming to come off as branches of it. 



In their progress the dark-bordered sentient fibres for the most 

 part tend towards the outer or cutaneous surface of the thin muscle, 

 on reaching which they branch out upon it underneath a thin 

 fascia, which covers the muscle and forms also the wall of an adjacent 

 lymph-space. 



The terminations of these sentient nerve-fibres were not seen by 

 Reichert, and doubtless because he used potash in his examination 

 of them ; but with the aid of some of the reagents already mentioned 

 they may be traced out, although from their extreme tenuity and 

 paleness this is no easy matter. Their mode of termination is on 

 the whole similar to that of the motor nerves, only the pale end- 

 fibres have a more extended distribution and are much finer. The 



of the cutaneous muscle ; 6, e, d, sentient fibres (truncules) to upper and middle 

 part of muscle, and e,f, to lower part, all dividing into finer terminal filaments 

 connected with nuclei which are not represented in this general view ; h, h, h, h, 

 branches of/ which went to abdominal muscles ; i, i, i, swollen parts of muscular 

 fibres containing ' nerve-tufts.' 



