1886.] on the Sympathetic Nervous System. 537 



are closely connected with the motor fibres which arise from the 

 lateral horn, e. g. the chorda tympani and the facial. Undoubtedly 

 this particular group of muscles has some closer relationship to the 

 viscera than other trunk muscles, and that relationship is explained 

 immediately if we can accept and extend van Wijhe's investigations, 

 viz. that in the cranial region the muscles which are supplied by the 

 third, fourth, sixth, and twelfth cranial nerves are derived from the 

 myotomes, while the muscles supplied by the seventh and fifth 

 cranial nerves are derived from the lateral plates of mesoblast. 



In fact, we may look upon the body as composed of two parts — 

 an outside or somatic part, and an inside or splanchnic part. Each 

 part has its own system of voluntary muscles ; each part is supplied 

 by nerves arranged on the same plan, viz. a ganglionated and non- 

 ganglionated portion ; and each part has its own individual centres of 

 action, the inside portion of the grey matter of the spinal cord con- 

 taining the centres for the splanchnic roots (2, 3, 5, in Fig.), i. e. the 

 centres of organic life ; the outlying horns the centres for the somatic 

 roots (1 and 4), i. e. centres for the animal life. It is a strange and 

 suggestive fact that these two sets of centres are not arranged sym- 

 metrically along the spinal axis, but that two great breaks occur in 

 which the centres of organic life fall into the background in com- 

 parison to those of animal life. These two great breaks correspond 

 to the origin of the nerves for the legs and arms, and suggest that 

 the formation of the limbs in the originally symmetrical ancestor of 

 the vertebrata — i. e. the large outgrowth of somatic elements in two 

 definite portions of the body, caused of necessity a corresponding 

 increase in the centres for animal life, while there was no necessity 

 for a corresponding increase in the centres for organic life. The 

 oldest part of us is undoubtedly the vital part ; those organs and 

 their nervous system by which the mere act of existence is carried on. 

 With these two there may have been originally a symmetrical seg- 

 mental arrangement of locomotor organs. Such symmetry, however, 

 went for good when it was found more convenient to concentrate the 

 locomotor machinery into the anterior and posterior extremities and 

 with the asymmetrical arrangement of the locomotor organs disap- 

 peared also the symmetry of the central nervous system. This cor- 

 respondence between the plan of the central nervous system and the 

 development of the extremities is to my mind strongly in favour of 

 the view which I have put before you to-night. In conclusion, I 

 thank you for the kindness with which you have listened to me, and 

 hope that I have succeeded in convincing you that Bichat's teaching 

 of an independent sympathetic system is finally dead. 



[W. H. G.] 



