MUSCLES. 



363 



smaller than the other; and that those of the medium size, although 

 not larger than the ninth part of a very delicate hair, are composed of 

 one hundred filaments. He supposed the ultimate filament to be always 

 of the same size. Prochaska 1 says, that the ultimate fibre or filament 

 is discernible, and that its thickness is about the ^th part of the dia- 

 meter of the red globules of the blood ; and MM. PreVost and Dumas, 2 

 from the result of their microscopic observations, afiirm, that 16,000 

 fibres may be contained in a cylindrical nerve, one millimeter or 0-039 

 of an inch, in diameter. The microscopic examinations of Mr. Skey, 3 

 which have been confirmed and developed by subsequent observers, led 

 him to infer, that there is a distinction between the muscular fibres of 

 animal and organic life; the former having, in man, an average diameter 

 of ^Jffth f an i ncn - Each of these muscular fibres is -divisible into 

 bands or fibrillse, and each of these is again subdivisible into about 100 

 tubular filaments, arranged parallel to each other: the diameter of each 

 filament is yg^oir^ 1 P ar t of an inch, or about a third part of that of a 

 blood-globule. The muscles of organic life he found to be composed, 

 not of fibres similar to those described, but of filaments only; these 

 filaments being interwoven, and forming a kind of untraceable net- work. 

 The fibres of the heart appeared to possess a somewhat compound cha- 

 racter of texture : the muscles of the pharynx exhibited the character 

 of those of animal life, whilst those of the oesophagus, stomach, intes- 

 tines, and arterial system possessed the character of those of organic 



Fig. 144. 



Fig. 145. 



Non-striated Muscular Fibre. 



At 6, in its natural state. At a, showing the 4. A muscular fibre of organic life, with two 



nuclei after the action of acetic acid. of its nuclei ; taken from the urinary bladder, and 



magnified 600 diameters. 5. Muscular fibre of or- 

 ganic life from the stomach, magnified the same. 



life. He was^ unable to determine the exact nature of the muscular 

 fibres of the iris. At the present day, muscular tissue is universally 



1 De Carne Muscular!, p. 25, Vienn., 1778. 



2 Annales de Chimie, tom.xviii.; Magendie's Journal de Physiologic, torn. iii. 



3 Transactions of the Royal Society, for 1836. 



