On muscular Motion. \\g 



in the reticular membrane, the common covering of all the 

 different substances in an animal body, and the connecting 

 medium of all dissimilar parts. 



By this simple disposition, the medullary substance of 

 nerve is spread through all organized, sensible, or motive 

 parts, forming a continuity which is probably the occasion 

 of sympathy. Peculiar nerves, such as the first and second 

 pairs, and the portio mollis of the seventh, terminate in an 

 -expanse of medullary substance which combines with other 

 parts and membranes, still keeping. the sensible excess of 

 the peculiar medullary matter. 



The peculiar substance of nerves must in time become 

 inefficient ; and, as it is liable to injuries, the powers of re- 

 storation, and repair are extended to that material . The 

 reunion of nerves after their division, and the reproduction 

 alter part of a nerve has been cut away, have been esta- 

 blished by decisive experiments. Whether there is any 

 new medullary substance euiployed to fill up the break ; 

 and, if so, whether the new substance be generated at the 

 part, or protruded along the nervous theca from the brain, 

 are points undetermined : the history of the formation of 

 a fcEtus, the structure of certain monsters, and the organi- 

 zation of simple animals, all seem to favour the probabilitv 

 that the medullary matter of nerves is formed at the parts 

 ivhere it is required, and not in the principal seat of the 

 cerebral medulla. 



This doctrine, clearly established, wo\i1d lead to the be- 

 lief of a very extended commixture of this peculiar matter 

 in all the sensible and irritable parts of animais, leaving the 

 nerves, in their limited distribution, the simple office of con- 

 veying impressions from the two sentient masses with which 

 their extremities are connected. The most simple animals, 

 in whom no visible appearances of brain or nerves are to be 

 found, and no fibrous arrangement of muscles, may be con- 

 sidered of this description : Mr. John Hunter appeared to 

 have had some incomplete notions upon this subject, which 

 may be gathered from his representation of a materia vitte 

 in his Treatise on the Blood, &:c. Perhaps it would be 

 more proper to distinguish the peculiar matter of muscle 

 by some specific term, such, for example, as materia con- 

 tractilis, 



A particular adaptation for the nerves which supply the 

 electrical batteries of the torpedo and and gymnotus, is ob- 

 servable on the exit o-f each from the skull ; over which 

 there is a firm cartilage acting as a yoke, with a anuscle 

 affixed to it, for the obvious purpose of compression : so 

 H 4 that 



