52 LECTURE II. 



This general and imperfect sketch of the 

 anatomy of the nervous system, relates 

 only to what may be discovered by our 

 unassisted sight. If by means of the mi- 

 croscope we endeavour to observe the ulti- 

 mate nervous fibres, persons in general are 

 as much at a loss as when by the same 

 means they attempt to trace the ultimate 

 muscular fibres. 



Those fibres which we can split off 

 from a nervous packet, in the manner be- 

 fore mentioned, though too minute to ad- 

 mit of further subdivision, appear by the 

 microscope to be themselves packets of 

 smaller threads. It is generally asserted 

 by microscopical observers, that the nerves 

 and medullary matter of the brain and spi- 

 nal marrow are the same, and are com- 

 posed of very minute fibres. Fontana 

 speaks confidently on this point ; and he 

 further says, that he has seen these ner- 

 vous fibres regenerated in the medium 

 which has been formed to unite a divided 

 nerve. He describes the nervous fibres in 

 every part of the nervous system as cylin- 



