GENERAL ANATOMY OF MUSCLES. 281 



already apparent in the flexors and extensors of the fingers and 



toes. 



At the end of the fourth or fifth month, the muscles present 



a reddish aspect, and at the period of birth, though they may 



be readily dissected from each other, they are very soft, and of 



a color much less deep than those of the adult, 



Muscular fibres are connected to each other by cellular mem- 

 brane. This membrane surrounds each muscle; and its 

 various lamina, gradually diminishing in thickness, pass be- 

 tween the different bundles of fibres, and the different fibres of 

 which each muscle is composed. 



The fibres of muscles, when examined with magnifying 

 glasses, appear to be composed of fibrillae still smaller ; and it 

 has been supposed that this division of them extended beyond 

 our powers of vision, even when assisted by microscopes : but 

 so many errors have occurred in microscopical observations of 

 very minute objects, and so much difference exists between the 

 reports of different observers, that the subject at this time does 

 not interest many persons ; and very little attention is paid, by 

 the anatomists and physiologists of the present day, to the 

 opinions of those observers who supposed they had ascertained 

 the structure of the ultimate fibrillae. 



The cellular or recticular membrane investing the whole 

 muscle, is called the muscular sheath. It is formed round 

 every muscle of the body, but varies much in different places 

 in regard to thickness and strength. Each of the many larger 

 fasciculi) or bundles of fibres, (lacerti,) of which every muscle 

 is obviously composed, is surrounded in like manner by pro- 

 cesses sent inwards from the sheath, and is a perfect, though 

 diminutive representative of the entire muscle. 

 This secondary sheath surrounding the fasciculi, sends pro- 

 cesses likewise inwards, and invests and separates the indivi- 

 dual fibres so called, or rather the primitive fasciculi, of which 

 each larger fasciculus is formed. These fibres or primitive 

 fasciculi themselves are again susceptible of subdivision into 

 what are called the ultimate muscular filaments, between 

 which, it is probable, though not susceptible of demonstration, 

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