z The Introductiok. 



iiire^ it being a thin expanded Subftancey ivhich hiij 

 Length and Breadth, without much Thicknefs ; fo that it 

 feems only to be made up cf [ingle Threads ^ laid lengthways 

 and acrofsy like a fine JFeb. We find fame of them pretty 

 thick, efpe daily toiuards their Origin ; but others much thin- 

 ner than the Film of an Egg : The vjhole Body is ivrap'd up 

 in one ofthefe, and every particular Part has a membranous 

 Cover, ivhich prefcrves it from the Injuries it would be ex- 

 posed to from thole Parts ivhich lie next it. Some Parts are 

 invoh din double Membranes, as the Brain, and Pith of the 

 Back, i^c. ivhich are very foft and delicate, and could not 

 he eafily preferred by a fingle one. 



But befides their Office of covering and defending all Parts 

 cf the Body, fo)ne of thent ferve as 'Bags or Cafes for 

 Food and Excrements ; others are formed into Conduits, for 

 the Blood and animal Juices. But fome of thefe being part- 

 ly mu/ciilar, and partly membranous, they may be properly 

 faid to be of a mix'd Nature, as are mojl of the Mufclcs, 

 and many other Subjlances throughout the Body. 



The Mufcles are made up of fiej})y and tendinous Fibres ; 

 *which Kind of Structure is necejfdry to their Action, they 

 being the Injiruments of Motion. Almoft all Mufcles are 

 flej])y and foft in the Middle, and for that Reafonare capable 

 of being contracted and dilated ; J or if they were other wife. 

 It ivould be impojibk for any Creature to move : Whereas 

 by the Figure they are cf, tve find them ready to anfwer 

 every Inclination of the Mind., ivitheut Pain or Stijfnefs. 

 The Mufcles are of different Figures, fome flat, as thc/'e on 

 the Rim of the Belly ; others more round, as thofe of the 

 Thighs and Legs ; jome of which, toivards their Injertions, 

 terminate in a (irong, 7iervous, ftne-ixy Subjlance^ tailed a 

 Tendon. 



A Ligament is more compact and firm than a Tendon, 

 but not altogether fo hard as a Cartilage. It is that 

 Subjlance which ties the "Joints together ; whereof jome are 

 rou^.d, as thofe ivhich ave obfervefajhned to the Head of a 

 Bone, and the Infide of its Socket ; ethers are fiat, and co- 

 ver the Joints like fo many Pieces of Leather nail' d on , to 

 keep the two Bones from falling afunder, and to pre ferve an 

 Uniformity in their Motion. 



A Cartilage, or Griftle, which we obferve more or lefs 

 at the Ends of mofi Bones, is harder and lefs pliable than 

 the Ligaments : Thefe being of a fmooth Surface, and 

 moderately thifk, are a Defence to the Ends of the Bones^ 



•which 



