478 MUSCLES. 



elastic filaments could form lines so sharply angled ; that he him- 

 self could not distinguish by the microscope which filament be- 

 longed to nerve and which to muscle ; and that, if MM. Prevost 

 and Dumas did see something like what they represent, their ex- 

 periment was worth nothing, because, the muscular lamina being in 

 contact with the object-holder in many points, any tremor caused 

 mechanically or by galvanism applied to the nervous fibre would 

 produce sinuous movements which afterwards were supposed 

 more or less regular and angular. In short, he truly says that 

 the only rational mode of observation is with a living muscle in ac- 

 tion ; that he has carefully watched the contraction of the muscles 

 of the feet of gasteropoda, &c. and always found the fibre simply 

 shorten, its diameter increasing at the time and small swellings 

 appearing throughout its length. b 



Dr. Wollaston c states that muscular contraction is accompanied 

 by a vibratory sound like that of carriages passing rapidly over 

 a pavement at a distance ; and infers that it is not continuous but 

 intermitting, consisting of a number of contractions repeated at 

 extremely short intervals : and he fancied that such vibratory 

 alternations might be about twenty or thirty in a second. He 

 applied the ball of the thumb to the ear, pressing the end of 

 the thumb at the 'same time against the head. As soon as the 

 thumb is bent so as to press against the head, the noise is heard ; 

 and I find it far louder if both thumbs are used at once, and still 

 louder if the jaws are at the same time tightly closed. In regard, 

 however, to the intermittence of muscular action, a friend informs 

 me that the action of the muscles of the eye cannot intermit 

 even the 2000th part of a second, because, if a luminous point is 

 moved with rapidity perpendicularly, and the eye horizontally, 

 the luminous line is not a zigzag, as it would be were there inter- 

 missions, but perfectly continuous/ 1 



The muscles, voluntary and involuntary, of all animals in which 

 a nervous system has been discovered, contain nerves ; for the 

 will operates by encephalo-spinal nerves on the voluntary muscles, 

 and the stimulating contents of involuntary muscles do not act, 

 except by distension, directly upon them, but upon a membrane 



*> 1. c. 494. sqq. c Phil. Trans. 1810, p. 2. sqq. 



d Two curious cases are related in Drl James Johnson's Med.-Chir. Review, 

 Oct. 1834, of the action of muscles occurring with a cracking noise like that of 

 snapping joints, and with pain. 



