4-72 MUSCLES. 



synonymous with the two words muscular contractility ; but we 

 must regard the power as the same with that which produces the 

 motions of the minute vessels of all kinds of minute or gelatinous 

 animals, and those rapid motions of some animal and vegetable 

 parts which show no fibres, we must regard it as a form of ex- 

 citability. The term irritability should have a more extensive 

 meaning than excitability: for, while this implies motion, irri- 

 tability implies the general power of being affected by irritating 

 causes, whether manifested by direct motion or by other changes 

 which show either sensation or an operation distinct from what 

 is seen in inanimate bodies : it is in truth vital affectibility in the 

 largest sense. f 



" The muscles, which are the immediate organs of by far the 

 greater number of our motions, form the greatest bulk among all 

 the similar parts." 



" They are distinguished from other similar parts chiefly by two 

 characteristic features, the one derived from their structure, the 

 other from their remarkable powers. 



Their fleshy structure is formed of moving fibres, sui generis, 

 and of a very faint red colour, and every muscle may be resolved 

 into fibrous bands, these into bundles of fibres, and these again 

 into very fine fleshy fibres and fibrils. 



" Every muscle possesses a covering of cellular membranes, 

 which is so interwoven witn its substance as to surround the bands, 

 the bundles, and even each particular fibre and fibril. 



" Every part of the muscles is amply supplied with blood-vessels 

 and nervous threads. The latter appear to deliquesce into an 

 invisible pulp, and unite intimately with the muscular fibres : the 

 former are so interwoven with the fibres that the whole muscle 

 is red and acquires its own paleness only by being washed. 



"Most muscles terminate in tendons 11 , which are fibrous 1 parts, 

 but so different in colour, texture, elasticity, &c., as to be readily 

 distinguished from muscles : thus disproving the opinion of some, 

 that the tendinous fibres originate from the muscular. This 

 error arose chiefly from the circumstance of the muscles of infants 



f In my own use of terms, at note ( e ) p. 24, 25. supra, irritability and 

 irritation, should be substituted for excitability and excitement. 



* " See Ad. Murray, De Fascia Lata. Upsal. 1777. 4to." 



h " See Fourcroy, Mdmoires de TAcademie des Sciences de Paris , 1785, p. 392.; 

 and 1786. p. 38." 



8 " Albinus, Annotat, Academ. 1. iv. tab. v, fig. 2." 



