ELECTRICAL THEORY OF MUSCULAR CONTRACTION. 405 



some degree of contraction might not be excited by touching the unin- 

 sulated nerve, and having remarked, that contractions were most con- 

 stantly produced in the insulated nerve by a quick and light touch, he 

 adopted this method on an animal whose nerve was not insulated, and 

 frequently obtained slight contractions. All his experiments on this 

 subject seemed to prove, that, cseteris paribus, muscular contractions, 

 produced by the contact of a solid body with a nerve, are much less 

 considerable, or even wholly wanting, when the nerve, in place of being 

 insulated, is in communication with a good conductor ; and it would 

 seem to follow, as a legitimate conclusion, that these contractions are 

 dependent on electricity ; facts, which it is well to bear in mind, in all 

 experiments on animals where feeble electrical influences are employed. 1 

 Galvanic electricity, it will be seen hereafter, is one of the great 

 tests of muscular irritability, and is capable of occasioning contractions 

 for some time after the death of the animal, as well as of maintaining, 

 for a time, many of the phenomena peculiar to life. This is the reason 

 why muscular contraction, excited by this nervous, electroid fluid, has 

 been regarded as an electrical phenomenon. Much discrepancy has, 

 however, arisen amongst the partisans of this opinion regarding its 

 modus operandi. Rolando, we have seen, assimilates the cerebellum to 

 an electro-motive apparatus, which furnishes the fluid that excites the 

 muscles to contraction. Some have compared the spinal column to a 

 voltaic pile, and have supposed the contraction of a muscle to be owing 

 to an electric or galvanic shock. The views of MM. Dumas and Prevost 2 

 are amongst the most striking. By a microscope, magnifying ten or 

 twelve diameters, they first of 'all examined the manner in which the 

 nerves are arranged in a muscle; and found, as has been already ob- 

 served, that their ramifications always enter the muscle in a direction 

 perpendicular to its fibres. They satisfied themselves, that none of the 

 nerves really terminate in the muscle ; but that the final ramifications 

 embrace the fibres like a noose, and return to the trunk that furnishes 

 them, or to one in its vicinity, the nerve setting out from the anterior 

 column of the spinal marrow, and returning to the posterior. On farther 

 examining the muscles at the time of their contraction, the parallel 

 fibres composing them were found, under the microscope, to bend in a 

 zigzag manner, and to exhibit a number of regular undulations; such 

 flexions forming angles, which varied according to the degree of con- 

 traction, but were never under fifty degrees. The flexions, too, always 

 occurred at the same parts of the fibre, and to them the shortening of 

 the muscle was owing, as MM. Dumas and Prevost proved by calculat- 

 ing the angles. The angular points were always found to correspond 

 to the parts where the small nervous filaments enter or pass from the 

 muscles. (See page 371.) They therefore believed, that these filaments, 

 by their approximation, induce contraction of the muscular fibre; and 

 this approximation they ascribed to a galvanic current running through 

 them ; which, as the fibres are parallel and in proximity, they thought, 

 ought to cause them to attract each other, according to the law 



1 Coldstream, art. Animal Electricity, in Cyclop. Anat. and Physiol., P. ix. p. 93, Jan., 

 1837; and J. Miiller, Elements of Physiology, by Baly, p. 261, London, 1838. 



2 Journal de Physiologic, torn. iii. 301 ; and Magendie, Precis, i. 220. 



