CONTEACTION OF MUSCULAR FIBRE. 443 



ted variety, the bundle that has been disturbed alone contracts, ~ 



-, 1P ' Difference in 



and presently alter relaxes ; but there is no lateral spread or the contrac- 

 diffusion of the effect to adjacent bundles, except in the case teTlndton-" 

 of the heart, in which it would appear that the contraction of striated mus- 

 one part is diffused laterally, and a single disturbance is fol- cles ' 

 lowed by many alternating contractions and relaxations, simulating, as it 

 were, the normal function of the whole organ. But where the non-stria- 

 ted form is in like manner examined, the contraction takes place more 

 slowly, spreads laterally to a wider extent, and is followed by a relaxa- 

 tion. The effect of an intermitting magneto-electric current is different 

 in the two forms of tissue, the striated contracting and keeping Effect of 

 contracted as long as the action is kept up, but the effect ceasing electrical 

 when the current stops. In the non-striated the action is tardy, 

 and relaxations may ensue even while the current is passing, and con- 

 tractions continue to occur after it has stopped. The effect becomes of 

 more interest when a weak, continuous electrical current is passed through 

 the centrifugal nerves supplying any muscle, for then the whole muscle 

 contracts, and remains in that state as long as the current flows. If the 

 current be passed through the ganglionic centre of those nerves contrac- 

 tion again ensues, and is maintained for a time even after the current has 

 ceased. If the current be sent through the centripetal fibre, alternate 

 contractions and relaxations of the muscle are the result. The interpret- 

 ation of these different cases has already been given (p. 276). 



The capability of contracting continues in muscle fibre for a certain 

 time after death, a period which is shorter as the rate of res- Experiments 

 piration is higher, and hence these effects were first observed of Gaivani. 

 by Gaivani and others in the case of the frog and cold-blooded animals. 

 Even after it has disappeared, it may be re-established by Ex eriments 

 continuing the supply of arterial blood, as Dr. Brown- Sequard of Brown-Se- 

 has shown : a fact which illustrates in a striking manner the quai ' 

 independence of the muscular contraction of the nervous system. Of 

 course, as would have been expected, whatever interferes with due arte- 

 rialization* interferes with muscular power. This is the reason of the 

 inability for exertion which is experienced in the thin air of mountain 

 tops, the relaxation of the muscular system in asphyxia, the same con- 

 dition in the respiration of the vapors of ether or of chloroform ; it is also 

 to a great extent the cause of the wayward and staggering gait of the 

 drunkard. The converse of this likewise holds good : the higher the rate 

 of respiration, the more energetic the muscular power ; and therefore, in 

 birds, which respire most perfectly, muscular contractility is exhibited 

 with the greatest energy. 



The contractility of the muscular tissues, as being independent of the 

 activity of the nervous system, is well illustrated by the remarkable ob- 



