MUSCLES. 477 



each cylinder is '002 of an inch in diameter, and slightly crimson.* 

 A bundle of cylinders is enveloped in a membrane ; and such 

 masses are enveloped in another membrane ; these larger masses 

 in others ; till all have one general outer covering, which is usually 

 white and hard towards its extremities, and terminates in a white 

 shining chord called tendon and inserted into periosteum. 11 The 

 fibres of tendon are said to be really solid, of infinitely smaller 

 diameter, and disposed in a reticulated manner. Even cellular 

 membrane is said to consist of reticulated tubular fibres, yj^ of 

 an inch in diameter on the average, and exhibiting transverse con- 

 tractions. x Fontana, by means of glasses of moderate powers, 

 found tendon to be composed of bands, which again are com- 

 posed of solid spiral cylinders, of uniform size, and pursuing a 

 tortuous course.? 



M. M. Prevost and Dumas assert that the muscular fibres, straight 

 while at rest, approximate each other at intervals, under con- 

 traction, so as to acquire a zigzag course ( WW) an( ^ shorten 

 the distance of their two extreme points 2 ; and thus Dr. Hales re- 

 marked that, when the abdominal muscles of a frog contracted, 

 " the scene instantly changed from parallel fibres to series of rhom- 

 boidal pinnulae, which immediately disappear as soon as the muscle 

 ceases to act." a They ascertained satisfactorily that during con- 

 traction no increase of volume is acquired If muscles, while the 

 fibres are straight, are stretched still more, as continually hap- 

 pens in the muscular coats of cavities, the subsequent shrinking 

 to the original dimensions is unattended by the zigzag appear- 

 ance. Nervous filaments, they also assert, go perpendicularly to 

 the muscular fibre at the very points where the angles are formed 

 under the zigzag contraction, and yet not to terminate there or 

 unite with the muscular fibres, but to return to the same nerve or 

 anastomose with other nerves. The approximation of the nerv- 

 ous filaments to each other is thought to draw the muscular 

 fibres into angles, and thus be the cause of muscular con- 

 traction. But Raspail objects that it is hard to conceive how 



* " The ultimate muscular filament has been estimated at ^^ of an inch in 

 diameter : their union forms fasciculi. Prochaska says that 200 fasciculi form 

 a bundle ; these are from $ to -^ of an inch in diameter." Dr. Tiedemann, 

 1. c. p. 418. additional notes by Drs. Gully and Hunter Lane. 



u Nouveau Systeme, 490. sqq. 



x Mr. Hare, 1. c. p. 36. y Sur les Poisons, t. ii. p. 230. sq. 



z Dr. Magendie's Journal de Physiologic, t. iii. a Hcemastatics, p. 59. 



