38 



HANDBOOK OF PHYSIOLOGY ^ NEUROPHYSIOLOGY I 



.<V. DIAGRAMS ILLCSTHATrNG THE ELEMENTARY 

 COMBINATIONS OF THE NERVOUS SYSTEM. 



r A 



FIG. 24. Above: Schema of the connections between the posterior and an- 

 terior roots of the spinal cord as taught to students in the days before the 

 neuron doctrine and the theory of the synapse. [From Bernard, C. Lemons 

 sur la Physiologie el la Palhologie du Sysleme .Nerveux. Paris: Balliere, 1858.) 

 Right: Connections in the nervous system as taught to students in 1885. 

 (From Pye-Smith, P. H. Syllabus of a course of lectures on Physiology delivered at 

 Guy's Hospital. London: Churchill, 1885.) 



Recognition of the synapse could come only after 

 the neuron theory had replaced the reticular theory. 

 According to the latter, strongly championed by 

 von Gerlach (211), nerve cells were connected with 

 each other by a diffuse fibrillary network forming an 

 anastomosis. This hypothesis received support from 

 Golgi (212), although it was his silver staining tech- 

 nique in the hands of Ramon y Cajal (213) that 

 finally disproved it, for Ramon y Cajal established 

 that both axons and dendrites had free endings. To- 

 gether they shared the Nobel prize in igo6, Golgi 

 devoting his address to an attack on the neuron theory 

 that his fellow prize winner had done so much to up- 

 hold. In modern times, the synapse (an abstraction) 

 is having to be remodelled in the light of what the 

 electron microscope is revealing. 



The nature of central inhibition, a still incompletely 



211. VON Gerlach, Joseph (1820- 1896). The spinal cord. In: 

 S. Strieker, A Aianual of Histology (English translation). 

 London: New Sydenham Society, 1872. 



212. Golgi, Camillo (1844-1926). Atti Soc. ital. progr. sc. 

 3rd reunion. 1910. 



213. Ramon y Caj.\l, Santiago (1852- 1934). Neuron theory 

 or reticular theory. Arch. Jisiol. 5, igo8; translation by 

 Purkiss and Fox. Madrid, 1954. 



resolved issue, has e\oked many hypotheses. Among 

 them, those depending on mutual interference of 

 impulses at the effector component of the reflex arc 

 form one class. An example is the schema suggested 

 by Rosenthal (214) in 1862 to explain the effect of 

 efferent vagus fibers on the respiratory center. He 

 proposed that an effector system excited into action 

 by one nerve could have the pulsating rhythm of its 

 nervous supply disturbed by inflow from another 

 nerve, the result being a redistribution of previously 

 grouped impulses into more frequent but less powerful 

 (and hence inadequate) discharges. Lack of evidence 

 for a pulse-like time-rhythm in nerve trunks led to the 

 rejection of this hypothesis by W'undt, Sherrington 

 and others. 



In the 1870's and 1880's attempts to explain inhi- 

 bition on metabolic effects depending directly on the 

 cell's response to stimulation being an assimilation of 

 chemical nutrients were espoused by Gaskell (215) 



214. Rosenthal, Joseph. Die Atembeweg und ihre Bezichung zum 

 nervus Vagus. Berlin, 1862. 



215. Gaskell, Walter Holbrook (1847-1914). On the 

 rhythm of the heart of the frog and of the nature of the 

 action of the vagus nerve Phil. Trans. 173; 993, 1882. 



