116 On muscular Motion. 



from the preceding fact, like the uUimate organization of 

 the simpler classes. 



It is obvious that the muscles of birds are formed out of 

 the albumen ovi, the vitellus, and the atmospheric air, acted 

 upon by a certain temperature. The albumen of a bird's 

 esrg is wholly consumed during incubation, and the vitellus 

 liule diujinished, proving tliat the albumen contains the 

 principal elementary materials of the animal thus generated; 

 and it follows that the muscular parts, which constitute 

 the greater proportion of such animals when hatched, are 

 made out of the albumen, a small portion of the vitellus, 

 and certain elements, or small quantities of the whole com- 

 pound of the atmosphere. 



The muscles of birds are not dlflcrent, in any respect, 

 from those of quadrn))eds of the class of mammalia. 



The anatomical structure of muscular fibres is generally 

 complex, as. those tibves are connected with membrane, 

 blood-vessels, nerves, and lymphaeducts ; which seem to 

 be only appendages of convenience to the essential matter 

 of muscle. 



A muscular fibre, duly prepared by washing away the 

 adhering extraneous substances, and exposed to view in » 

 powerful microscope^ is undoubtedly a solid cylinder^ the 

 covering of which is leticular membrane, and the contained 

 part a pulpv substance irregularly granulated, and of little 

 cohesive power when dead. 



A difficulty has often subsisted among anatomists, con- 

 cerning the ultimate fibres of muscles ; and, because of their 

 tenuity, some persons have considered them infinitely di- 

 visible; a position which may be contradicted at any time 

 bv an hour's labour at the microscope. 



The arteries aiboresce copiously upon the reticular coat 

 of the muscular fibre, and in warm blooded animals these 

 vessels are of sufficient capacity to admit the red particles 

 of blood ; but the intrinsic matter of muscle, contained 

 within the ultimate cylinder, has no red particles. 



The arteries of muscles anastomose \\ ilh corresponding 

 veins ; but this course of a continuous canal cannot be sup-, 

 posed to act in a direct n)anner upon the matter of muscle. 



The capillary arteries lerniinating m the muscular fibre 

 must alone eftcct all the changes of increase in the bulk or 

 number of fibres, in the replenishment of exhausted mate- 

 rials, and in the repair of injuries: some of these necessitie;* 

 may be supposed to be continually operating. It is well 

 known that the circulation of the blood is not essential to 

 muFcular action ; so tb.at the mode of distribution of the 



blood- 



