GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 27 



electrical, mechanical, thermal, and chemical. Evidently the muscle-proto- 

 plasm is irritable and is capable of developing 1 a contraction independently of 

 the nerves. There are a number of natural plant bases that have a " curare- 

 like" action — c. g. } brucin, strychnin, leucin, nicotin, conin, etc. 1 If a 

 nerve-muscle preparation be dissected out and placed in a 0.7 per cent, solu- 

 tion of sodium chloride containing one of these drugs, sooner or later the nerve- 

 ends will be poisoned, and it will be found that excitation of the nerve has no 

 effect on the muscle, although the muscle responds well to direct excitation. 



Other Proofs llutt the Muscle-protoplasm can be Directly Irritated. — Mus- 

 cles with long parallel fibres, such as the sartorius of the frog, contain no 

 nerves at their extremities, the nerve-fibres joining the 

 muscle-fibres at some little distance from their ends. 

 The tip of such a muscle, where no nerve-fibres can 

 be discovered by the most careful microscopical exam- 

 ination, is found to be irritable. The fact that in some 

 of the lower animals there are simple forms of contrac- 

 tile tissue in which nerves cannot be discovered, and 

 which are irritable, is interesting as corroborative evi- 

 dence, although it is not a proof, of the independent 

 irritability of a highly differentiated tissue such as 

 striated muscle. Another similar piece of evidence is 

 to be found in the fact that the heart of the embryo 

 beats rhythmically before nerve appears to have been 

 developed. A proof can be found in the observation 



that if a nerve be cut it begins to undergo degenera- Fl «- 4 --curareexpenment: 



& ... the shaded parts shovi there 



tion and loses its irritability and conductivity in four gionofthebody to which the 



or five days, and the excitation of such a nerve has S^^fSS*™ 



no effect upon the muscle although direct stimulation protected by the ligature 



,. ri i •, Mf • r> ii ii ,• » from the action of the drug. 



Of the muscle itself IS followed by contraction. As The unbroken lines represent 



degeneration involves not onlv the whole course of the the sensory nerves which 



... " , . . carry sensorv impulses from 



nerve, but also the nerve end-plates, the contraction the skin to the central nerv- 



must be attributed to the irritability of the muscle- ous system ; the broken lines 



* m m indicate the motor nerves, 



substance. Another point of interest in this connection which carry motor impulses 



is the behavior of a dying muscle. If it be struck, &om the central nervous sys- 



* o 7 t e]ll ,,,,( (I, (i R , muscles 



instead of contracting as a whole it contracts at the Lauder Brunton: Pharmacol 

 i i •. • •■ ■ j ,i j • ,i t} otii/. Therapeutics, ami M 



place where it was irritated, the drawing together ot „,,/„.<,) 

 the fibres at the part forming a local swelling, or welt. 



If such a muscle be stroked, a wave of contraction spreads over it, following 

 the instrument, instead of extending, as under normal conditions, by mean.- of 

 the excited nerve-fibres to other parts. Under these circumstances the circum- 

 scribed contraction would seem to show that the nerves had lost their irrita- 

 bility, or that the nerve-ends no longer transmitted the stimulus to the muscle, 

 and the response was due to the direct excitation of the dying muscle-fibres. 

 This phenomenon is known as an idiomuseiilar contraction. 



1 Santesson : Archiv fur experimentelle Pathologic und Pharmakologie, 1 '.<•">, Bd. 35, S. 23. 



