IMPROVER 89 



Motion of call the Nerves, unlefs of thofe which 

 are deftined to move the Heart and Breaft. But 

 the Reafon why the Motions of the Heart, and 

 Thorax or Breaft remain, and the Pulfe and Re- 

 fpiration continue, when the other Parts are de- 

 prived of Motion, is, becaufe in every Motion, 

 which is performed by Mufcles having Antagonifts 

 or others of contrary Motions to themfelves, a 

 Quantity of Nervous Fluid muft be derived into 

 the Contracting Mufcle, not only equal to that 

 which is derived at the fame Time into the Antago- 

 nift, but greater alfo. But leaft I may not be un- 

 derftood by the Word Mufcle, I fhall endeavour to 

 explain this Anatomical Term as plainly as may be. 

 And firft I fay. 



A Mufcle,' is a Bundle of thin and parallel Plates A Mufcle, 

 of flelhy Threads or Fibres, inclofed by one com- what. 

 mon Membrane, and all the Fibres or Threads of 

 the fame Plate, are parallel to one another, and 

 tied together at extremely little Diftances, by Ihort 

 and tranfverfe Fibres. Thefe flefhy Fibres are conv- 

 pofed of other fmaller Fibres, inclofed likewife by a 

 common Membrane or thin Skin : Each leffer Fi- 

 bre conftfts of very fniall Veiicles or Bladders, 

 into which we fuppofe the Nerves, Veins, and Ar- 

 teries, to open ;. for, every Mufcle receives Branch- 

 es of all thofe VeiTels, which muft be diftributed 

 to every Fibre. The two Ends of each Mufcle or 

 the Extremities of the Fibres, are, in the Limbs of 

 Animals, faftened to two Bones, the one of which 

 is m-oveable, the other fixed or immoveable : Arid 

 therefore, when the M^ifcles contradl, they draw 

 the moveable Bone according to the Direftion of 

 their Fibres. 



When the Mufcles contrail in Length, they 

 fwell in Thicknefs, as may be perceived by laying 

 the Finger upon the Majfetcr or Mufcle of the 

 lower-Jaw, and preffmg the Grinders or Axel-teeth 

 together : But this Power of Contracting or Swel- 

 ling is loft, when either the Artery, or Nerve of 



the 



