ARRANGEMENT OF THE NERVOUS SYSTEM 565 



CHAPTER XL VI 



THE FUNCTIONAL ARRANGEMENT OF THE NERVOUS 



SYSTEM 



The Neuron Doctrine. While the histological individuality of the 

 neuron has been founded upon the work of many investigators, it was 

 left to Waldeyer 1 to correlate the facts in such a way that clearness 

 was finally brought into the chaos of nervous elements and their func- 

 tion (1891). In accordance with the views of this investigator, the 

 neurons are to be regarded as the building stones of the nervous sys- 

 tem, and hence, must be dealt with as independent cellular units. 

 This implies that the nervous system is built up of individual neurons 

 which retain a definite structural relationship to one another. They 

 are connected with one another by means of their processes, but this 

 connection is had only by contact and not by confluence. 



We have noted that the neuron possesses an embryological dis- 

 tinctiveness in the form of the neuroblast. To this must now be 

 added its specific histological and anatomical appearance and thirdly, 

 also a definite functional independence. The sum total of their 

 individual actions gives rise to the complex of nervous processes as 

 we observe them in the higher animals. This extension of the neuron 

 doctrine to function followed very naturally upon the establishment 

 of the fact that neurons are structural entities. Physiologically, the 

 neuron concept tends to place emphasis upon the cytoplasm and nu- 

 clear constituents of the cell-body rather than upon the conducting 

 paths, so that the former must really be considered as the directing 

 element of the whole. 



The Fibrillar Hypothesis. Contrary to Waldeyer and his followers, 

 it is held by Nissl, 2 Bethe, 3 Apathy, 4 Schenck, 5 and Pfluger 6 that 

 the nervous system is made up of conducting strands of neuroplasm 

 which are directly continuous with one another. The element which is 

 thus brought into prominence, consists of the neurofibrils which, as 

 we have just seen, permeate the cytoplasm of the cell-body and go 

 to form the dendritic and axon processes of the neuron. In accord- 

 ance with this view, the structural and functional unit of the nervous 

 system is formed by the neurofibril. Here and there a number of 

 these fibrils may pursue a common course and form such structures 



1 Deutsche med. Wochenschr., 1891. Also see: v. Leuhosse"k, Der feinere Bau 

 des Nervensystemes, etc., Berlin, 1895; and Verworn, Das Neuron in Anat. 

 und Physiol., Jena, 1900 and Med. Klinik, 1908. 



2 Die Neuronenlehre und ihre Anhanger, Jena, 1903. 



3 Allg. Anat. und Physiol. d. Nervensystemes, Leipzig, 1903. 



4 Mitt, der Zool. Station zu Neapel, xii, 1897. 

 B Wiirzburger Abhandl., ii, 1902. 



6 Pfluger 's Archiv, cxii, 1906. 



