192 Oii MUSCULAR MOTION* 



confil-matlon of which would improve the knowled^ of animal 



^eftieration by (kewmg that it is gernrrtiferous. There are fuf- 



ficient analogies of this kind in nature, if reafoning frora 



analogies were proper for the prefent occafion. 



The punftum fallens, during its firft actions, is not encom-i 



palfed by any fibres dilcoverable with microfcopes, and the 



vaCcula'r fyftem is not then evolved^ the bJood flowing for^ 



wards and backwards,, in the fame veflels. The commence- 



ment of iife in animaJs of complex ftru6ture is, from the 



preceding fa6t, like the ultimate organization of the fimpler 



clades. ^' . ■ ■ '. » , 



Mufclcs of birds It is obvious that the mufcles of birds are formed out of the 



orthra?bumen ^^t)umen ovi, the vitellus, and the atmofpheric air, afted upon 



wlthafmall by a Certain temperature. The albumen of a bird's egg is 



and^atmt/S^ confumed during incubation,. -and the vitellus little di- 



miniihed, proving that the albumen contains the principal 



elementary materials of the animal thus generated ; and it 



follows that ihe mufcular parts, which conftitute the greater 



proportion of fuch animals when hatched, are made out of the 



albumen, a fmall portion of the vitellus, and certain elements, 



or fmall quantities of the whole compound of the atmofphere. 



and they do not The mufcles of birds are not different, in any refpecl, from 



oifhe mammalia! ^^^o^^ of quadrupeds of the clafs of mammalia. 



;-/The anatomical flrudure of mufcular fibres is generally 



complex, as thofe fibres are conne6led with membrane, blood- 



veffel?, nerves, and lymphasdufis ; which fcem to be only 



appendages of convenience to the eifcntial matter of mufcle. 



Mufcular fibre A muTcular fibre, 'duly prepared by wafliing away the ad- 



is cylindric; herinjf extraneous fubftances, and expoled (o view in a power- 

 membranous r . . . . 

 without, and ful micfofcope, is undoubtedly a folid cylinder, the covering 



pulpy withm. .^f which is reticular mdmbrane, and the; contained part a pulpy 

 fiibflance irregularly granulated, and of little cohefive power 

 when dead. 



The ultimate A difficulty has often fubfifted among anatomifts concerning 



the ultimate fibres of mufcles ; and, becaule of their tenuity, 

 fome perfons have confuiered tlrem infinitely divifible, a 

 poiition which may be Gontradi6led at any time, by an hour's 

 labour at the microfcope. 



Arteries. The arteries arborefce* copioufly upon the reticular coat of 



the mufcular fibre, and in warrn-blooded animals ihefe velfels 



