4 HANDBOOK OF ANATOMY 



and sympathetic. The cerebro-spinal, consisting of the brain 

 and spinal cord, is formed largely of grey matter, which con- 

 sists of the actual nerve cells, and sends distributing fibres in 

 every direction, so that each muscle receives both an efferent 

 and afferent branch. The sympathetic is an accessory system. 



The whole body is covered by a thin tough membrane called 

 the " deep fascia," which closely invests the muscles, and send& 

 down processes, or dividing septa, between them. From the 

 deep fascia and the intermuscular septa many of the muscles' 

 get additional origins, and in some cases muscles are inserted 

 into adjacent fascia as well as bones. Outside this is the super- 

 ficial fascia, a thin friable membrane enclosing fat in its 

 meshes. This fascia is also found in spaces between muscles, 

 bones, and organs to prevent jarring and give elasticity. Over 

 all is the skin, from which the hair and nails are developed. 



