122 PHILOSOPHY OF ZOOLOGY. 



of phosphate of lime. They are either connected with the 

 digestive system, as the teeth in the stomach of the lobster, 

 or the jaws and teeth of the Sea-Urchin, (Echinus,) or they 

 constitute a central support for the soft parts, as the bone 

 of the Cuttle-fish, or the stalk of the Sea-pen. 



CHAP. VIII. 



OK THE MUSCULAR SYSTEM. 



HAVING considered, in the two preceding chapters, the 

 integuments which invest, and the bones which support, the 

 animal frame, we are now prepared to consider the organs 

 by which motion is executed, constituting the muscular sys- 

 tem. 



The investigation of this class of organs, unfolds the 

 most singular mechanism of parts, and an infinite variety 

 of movements, enabling the animal to perform the internal 

 and external actions necessary to its existence. 



The muscles appear in the form of large bundles, con- 

 sisting of cords. These, again, are formed of smaller 

 threads, which are capable of division into the primary fila- 

 ments. Each muscle, and all its component cords and fila- 

 ments are enveloped by a covering of cellular membrane, 

 liberally supplied by bloodvessels and nerves. 



The primary filaments appear to be parallel, and to be 

 of very small demensions. PROCHASKA * found them 

 nearly 4 ^00 f an mcn 5 while Mr BAUER estimates them 

 at only 2U Vd5 or tne ^ ZG f tne globules of the blood, 

 when deprived of their colouring matter -f\ Differences of 



* " In meis experimentis maxima globula rubri sanguinis diameter com- 

 parata cum diametro fili carnei se habere videbatur ut 8 vel 7 ad 1 ; unde 

 concluditur filum carneum a globule rubro sanguinis superari crassitie sua 

 vicibus inter quadraginta ct sexaginta." Operum Minorum, pars 1. p. 198. 



t Phil, Trans. 1818, p. 175. 



