26 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



The relationship of the spinal cord to peripheral 

 nerves and to the rest of the central nervous system 

 could hardlv be understood until the structure of the 

 neuron had been learned. The period that saw the 

 great development of knowledge of cell structure came 

 with the high-power microscopes of the nineteenth 

 century. Before then descriptions of the finer elements 

 necessarily lacked exactness, though in 1767 Fontana 

 had given a good account'^ of the axis cylinder, and 

 there seems little reason to doubt that the bodies 

 Alexander Monro (129) saw in the spinal cord in 

 1783 were the anterior horn cells. Nerve cells were 

 certainly seen by Dutrochet (130) in 1824 though we 

 do not find a very exact description of them before 

 1833, when Ehrenberg (131, 132) published his find- 

 ings on the spinal ganglia of the frog. 



The visualization of axis cylinders on the one hand, 

 and of cell bodies on the other, still did not help the 

 physiologist very much in his search for understanding 

 of nervous connections. It was from the botanists that 

 the next lead came. The cell theory had a long history 

 among plant physiologists and its emphasis on the 

 role of the nucleus and the cellular matrix appealed 

 to microscopists who could see similar structures in 

 animal tissues. In 1837 Purkinje (133), working at 

 home for lack of a laboratory at the Universit>- of 

 Breslau where he was profes.sor, realized the .signifi- 

 cance of the ob.servations on plant tissues and sug- 

 gested that the cell theory might justifiably be ex- 



129. Monro, .\lex.\nder (secundus) (1733-1817). Observa- 

 tions on the structure and Junctions of the nervous system. 

 Edinburgh: Creech, 1783. 



130. Dutrochet, Rene Joachim Henri (i 776-1847). ^f- 

 ckerches anatomiques et physiolooiques sur la structure intime 

 des animaux et des vegetaux. Paris : Bailliere, 1 824. 



131. Ehrenberg, C. G. Notwendigkeit einer feineren mecha- 

 nischen Zerlegung des Gehirns und der Nerven. Ann. 

 Physik. u. Chem. 104: 449, 1833. 



132. Ehrenberg, C. G. Beobachtung einer unhekannten Structur 

 des Seelesorgans. BerHn, 1836. 



133. Purkinje, Johann Evangelista (1787-1869). Uber die 

 gangliose Natur bestimmter Hirntheile. Ber. Versamml. 

 deutsch. Natmjorsch. Artze, Prague 1837, p. 175. 



'^ "Le nerf est forme dun grand nombre de cylindres 

 transparents, homogenes, uniformes, tres-simples. Ces cylindres 

 paroissent formes, comme d'une parol, ou tunique tr& subtile, 

 uniforme, remplie, autant I'oeil peut enjuger, dune humeur 

 transparente, gelatineuse, insoluble dans I'eau. Chacun de ces 

 cylindres recoil une enveloppe en forme de gaine exterieure, 

 la quelle est composee d'un nombre immense de fils torteux." 

 Fontana. Traite sur le venin de la I'ipere. Florence, 1781.2 vol. 



tended from botany to zoology. Two years later 

 Schwann (134) marshalled the facts and crystallized 

 the idea in his classic monograph. 



For an understanding of function, knowledge of the 

 cell bodies was not enough. The nerve tracts were of 

 primary importance, and during this same period 

 histologists were finding that the medullated axon was 

 not the only kind of fiber. In 1838, in a little book that 

 was one of the last scientific texts to be published in 

 Latin, Remak (135) revealed the existence of non 

 medullated nerves. His work is illustrated by many 

 delicate drawings of cells from various parts of the 

 nervous system, mostly taken from ox and man. But 

 by 1865 phy.siologists knew that in addition to medul- 

 lated and nonmedullated nerves there were other 

 fibrous processes which Dieter's (136) work (published 

 posthumously) showed to be dendrites. In the saine 

 monograph there is a description of the glia. The cell 

 theory did not explain how all these fibrous structures 

 related to the cell body, and a student's thesis was one 

 of the early publications to take this step. In 1842 

 von Helmholtz (137), in the earliest of the many 

 brilliant contributions he made to physiology, estab- 

 lished the connection between peripheral nerve and 

 ganglia in invertebrates using the crab, von Helmholtz 

 was 2 1 years old when he wrote this inaugural thesis. 



The next major advance came in 1850 from Waller 

 (138) with his demonstration that axons degenerate 

 when cut off from their cell bodies and his conclusion 

 that the latter were their source of nutriment. The 

 development by Marchi & Algeri (139) of the osmic 

 acid stain for degenerating myelin sheaths gave the 

 physiologist a technique for tracing the nerve tracts. 



134. Schwann, Theodore (1810-1882). Mikroskopische Unter- 

 suchungen iiber die Ubereinstimmung in der Struktur und dem 

 Wachsthum der Thiere und Pflanzen. Berlin: Sander, 1839; 

 English translation by Sydenham Society, 1847. 



135. Rem.\k, Robert (181 5-1 865). Observationes anatomicae el 

 microscopuae de systematis nervosi structura. Berlin: Reimer, 

 1838. 



136. Dieters, Otto Friedrich Karl (1821-1863). Unter- 

 suchungen iiber Gehirn und Riickenmark des Menschen und der 

 Sdugetiere. Brunswick: Vieweg, 1863. 



137. VON Helmholtz, H. De Fabrica systematis nervosi Everte- 

 bratorum (Inaugural Thesis). 1842. 



138. Waller, .Augustus Volney (1816-1870). Experiments 

 on the section of the glossopharyngeal and hypoglossal 

 nerves of the frog, and observations of the alterations 

 produced thereby in the structure of their primitive 

 fibres. Phil. Trans. 140: 432, 1850. 



139. Marchi, V. and C. Algeri. Sulle degenerazioni discen- 

 denti consecutive a lesioni della corteccia cerebrale. Riv. 

 sper. Frernat H: 492, 1885. 



