THE MUSCULAR SYSTEM. 261 



tions of the muscles are due, and by Avliich tlicy are necessarily produced, 

 and I Avill merely offer the following remarks. There can be no doubt 

 that the contractility of the muscular substance is a proper and inherent 

 attribute, and only called into manifest action to a certain extent through 

 the nerves; whilst it is equally certain, that there are no facts which 

 conclusively demonstrate, that the striped muscles contract indepen- 

 dently of a previous nervous influence. What the processes are which 

 take place in the fibrils during the contraction is wholly doubtful; but 

 it is to be hoped that the further investigation of the laws of the electric 

 currents in the muscles, prosecuted in the way so successfully pursued 

 by Du Bois Reymond (" Untersuchungen liber thier. Electricitat," Ber- 

 lin, 1848-49),* will throw some light upon this, as yet, obscure subject. 

 It would be more than bold to hazard an assertion with respect to the 

 nature and mode of action of the nerves upon the muscles, since we are 

 quite as much in the dark as to the processes which take place in the 

 nerves, as we are with regard to those occurring in the muscles them- 

 selves. From the anatomical facts, which prove, that in many animals 

 the motor nerve-fibres come in contact with each primitive muscular 

 fasciculus only at a few points, and never penetrate into its interior, it 

 is, however, rendered evident, that in the contraction of a muscle, the 

 nervous influence must act from a certain distance. 



The muscles also possess sensibility, though of a rather peculiar kind, 

 because punctures, burns, and incisions into their substance, excite 

 scarcely any sensations worth naming, whilst every muscle, after long- 

 continued activity, as well as when affected with cramps or spasms, be- 

 comes painful and very sensitive to pressure. They are also endowed 

 ■with an extremely delicate sense of feeling for their own state of con- 

 traction, so that they are capable of estimating very minute variations 

 in the force with which they act. The apparent contradiction between 

 these facts is easily accounted for, by the consideration that the muscu- 

 lar nerves contain but very few sensitive fibres, as is readily shown in 

 the nerves of the orbital muscles, &c. These fibres, to which probably 

 belong the few filaments above described, which are distributed over the 

 whole muscle, though too scanty to render a muscle sensible to local im- 

 pressions, nevertheless sufl^ice, when implicated in the contraction of the 

 entire muscular substance, to convey to the sensorium the degree of 

 pressure to which they are subjected, and, when the organs are over- 

 exerted, to induce pain, in consequence of the frequently-repeated irri- 

 tation which they have undergone, or of the compression they endure 

 from the rigidity of the muscle. 



The mechanical relations of the muscles have been excellently treated 

 of in the article by E. Weber (1. c), from which the following conclusions 

 may be drawn. The extent of the shortening of the muscles amounts, 



* Translated by Dr. Jones, London, 1S53. 



