50 



INTRODUCTION TO NEUROLOGY 



of any part of the neuron affects the welfare of the whole, and 

 the destruction of the nucleus and cell body destroys the entire 

 neuron, but such injuries do not directly affect adjacent 

 neurons. 



6. The neuron is a functional unit or, better, the functronal 

 unit of the nervous system. 



Fig. 14. Neurons from the trapezoid body of the medulla oblongata of a 

 cat, illustrating different forms of synapse: a, Delicate pericellular net 

 around the cell body of a neuron which is not shown; b, coarser endings; c, 

 still coarser net; d, calyx-like envelope. In b, c, and d, at the left of the 

 figure, the globular cell body of the neuron of the second order is shaded 

 with lighter stipple than the terminals of the axon of the neuron of the first 

 order. (After Veratti, from Edinger's Vorlesungen.) (It should be noted 

 that in this account we do not follow Veratti 's interpretation of these 

 structures, but that of Held, Ram6n y Cajal, and the majority of other 

 neurologists.) 



These six propositions are accepted in their entirety by many 

 neurologists; but it should be clearly understood that all of 

 them are controverted by others. The fourth proposition, in 

 particular, has been the subject of violent attack (see the dis- 

 cussion of the synapse below). The neuron, moreover, is a 

 functional unit (proposition 6) in only a rather limited sense 

 (see p. 56). Without further discussion of the merits of these 



