ORIGIN OF THE NERVOUS SYSTEM 263 



afford the material basis of the intellectual life. Thus in the verte- 

 brates the primary sensory and motor neurones in number and impor- 

 tance are outstripped by the association neurones. 



As thus sketched the development of the adjuster or central nervous 

 element of the neuromuscular mechanism takes place in the region 

 between the receptors and the effectors and in time after these two sets 

 of organs have appeared. Its primary function is undoubtedly trans- 

 mission involving the principle of the common path; secondarily it 

 comes to be a repository of the effects of nervous stimulation whereby 

 its principal function as a modifier of impulses is made possible. 



References 

 Apathy, S. 



1897. Das leitende Element des Nervensystems und seine topographischen 

 Beziehungen zu den Zellen. Mitth. zool. Stat., Neapel, Bd. 12, pp. 495- 

 748, Taf. 23-32. 

 Bethe, A. 



1897. Das Nervensystem von Carcimis Manas. Arch. mik. Anat., Bd. 50, 

 pp. 460-546, Taf. 25-30. 

 Fbiedlandeb, B. 



1894. Altes und Neues zur Histologic des Bauchstranges des Regenwurms. 

 Zeitschr. wiss. Zool., Bd. 58, pp. 661-693, Taf. 40. 

 Havet, J. 



1901. Contribution a l'etude du Systeme nerveux des Actinies. La Cellule, 

 tome 18, pp. 385-419, pis. 1-6. 

 Loeb, J. 



1894. Beitrage zur Gehirnphysiologie der Wurmer. Arch. ges. Physiol., 

 Bd. 56, pp. 247-269. 

 Nobman, W. W. 



1900. Do the Reactions of the Lower Animals against Injury indicate Pain 

 Sensations? Amer. Journ. Physiol., vol. 3, pp. 271-284. 

 Shebbington, C. S. 



1906. The Integrative Action of the Nervous System. New York, 8vo, 

 xvi + 411 pp. 



