PROPERTIES OF MUSCULAR FIBRE. 285 



was asserted by Mr. Earle (and the statement has been repeated by Mil Her) 

 that, if the irritability of a muscle, whose nerves have been divided, be 

 exhausted by repeated stimulation, it cannot be recovered. Dr. J. Reid has 

 shown, however, that the means employed by Mr. E. to exhaust the irrita- 

 bility were such as would probably induce an inflammatory condition of the 

 muscles, and would thereby interfere with the nutritive processes, which 

 would be necessary to re-establish the irritability during the state of subse- 

 quent quiescence. And he has further proved, that if the contractility be 

 exhausted by means which have no such unfavourable tendency, and the 

 other conditions favour the normal performance of the nutrient processes, the 

 irritability is restored, and remains for some time. His first experiments were 

 on cold-blooded animals, and they would in themselves be sufficiently satisfac- 

 tory ; but he has since repeated them in the Rabbit, and established the fact 

 beyond all doubt.* " The sciatic nerve was divided in the Rabbit, and a por- 

 tion of it removed. One wire from two galvanic batteries, consisting of thirty 

 pairs of plates, was applied over the course of the nerve ; and the other wire 

 was applied over the foot, which was kept moist, until the muscles had ceased 

 to contract. Three days after this, a weaker battery was used, and the mus- 

 cles of the limb had recovered their contractility, and contracted powerfully. 

 The more powerful battery was used as before, until the muscles had ceased 

 to respond to the excitement ; and three days after this, they had again recov- 

 ered their contractility." It seems scarcely possible to draw any other infer- 

 ence from these experiments than that Contractility is a property inherent in 

 Muscular tissue, and that the agency of the Nervous system upon it is merely 

 to call it into active operation. 



384. The second doctrine above referred to ( 380), as having been taught 

 by some physiologists, is that Muscles, though not dependent on nerves for 

 vital power, are yet dependent upon them for the exercise of that power, 

 all stimuli, which excite muscles to contraction, operating first on the nervous 

 filaments which enter muscles, and through them on the muscular fibres. 

 The facts which have been already stated, in regard to the ordinary action of 

 the Muscles of Organic life, furnish a sufficient answer to this hypothesis. It 

 is with great difficulty that these can be made to display their irritability, by 

 any stimuli applied to their nerves ; whilst they manifest it strongly, when 

 the stimulus is directly applied to themselves. Even in the Muscles of Animal 

 life, individual fasciculi may be thrown into action in the same manner; 

 although the entire mass cannot be put into combined operation, except by a 

 stimulus simultaneously communicated to the whole, which the nerve affords 

 the readiest means of effecting. Perhaps the most satisfactory disproof of it, 

 however, is to be found in the observation of Mr. Bowman, already cited 

 ( 371), that a single fibre, completely isolated from all its connections, may 

 be seen with the microscope to pass into a state of contraction, under the influ- 

 ence of direct irritation. Further, it has been experimentally ascertained, 

 that there are some chemical stimuli, which will produce the contraction of 

 muscles when directly applied to them, but of which the influence cannot be 

 transmitted through the nerves ; this is especially the case with regard to 

 acids. 



385. When all these considerations are allowed their due weight, we can 

 scarcely do otherwise than acquiesce fully in the doctrine of Haller, which 

 involves no hypothesis, and which is perfectly conformable to the analogy of 

 other departments of Physiology. He regarded every part of the body which 

 is endowed with Irritability, as possessing that property in and by itself; but 

 considered that the property is subjected to excitement and control from the 



* Loc. cit. 



