Bawden, Movements of the Netirone. 245 



Golgi's and Ramon y Cajal's beautiful preparations, that the neurones 

 of the cortex do not form a continuous pathway for the nervous im- 

 pulse, but that these are related only by the simple contiguity of their 

 terminal arborizations. The central mechanism for the simplest reflex 

 can thus no longer, he says, be conceived of as a single cell, but is 

 rather a relation of contact (" I'articulation a distance ") between these 

 terminal arborizations. Those chemical substances, then, such as 

 strychnine and potassium bromide which modify the reflexes operate, 

 not on the cell body, so much as on these prolongations of the cell. 

 This is the case also with curare, which has been shown to have its ef- 

 fect exclusively in the terminal arborizations of the motor nerve. ^ 

 Now if this conception is extended to all the nervous centres we are 

 in a better position, says Duval, to understand the anatomical or histo- 

 logical conditions of all such phenomena as memory, association, im- 

 agination, and even habit and education. In a similar way the accel- 

 erative effects of tea and coffee are explained. He refers to the papers 

 of Tanzi and Wiedersheim in support of his theory and cites also the 

 fact of changes in the cilia of the olfactory cells. The phenomena of 

 sleep are explained in the same way. When one falls asleep the ter- 

 minal prolongations of the neurones are supposed to retract. Feeble 

 stimulation of the sleeping man calls forth certain reflexes perhaps, but 

 is not sufficient to establish a full connection of the lower centres with 

 the cortex. Stronger stimulation, however, has the effect of securing 

 the elongation again of these contracted branches of the neurones. In 

 consequence, the connection with the cortex is re-established and the 

 person awakes. The successive stages of awakening mark the gradual 

 reestablishments of these cortical connections after this period of inter- 

 ruption of greater or less duration which we call sleep. In support of 

 the theory on the pathological side, reference is made to the researches 

 of Azoulay (6) on general paralysis, studied by the Golgi-Cajal method, 

 in which a part of the dendritic ramifications of the pyramidal cells 

 had disappeared — that is, the pseudopodia of certain neurones had 

 become atrophied. He cites also the researches of Balbiani and of 

 Morat (71). 



Langley's investigations (55) on the action of various poisons on 

 the nerve cells and nerve endings in the frog's heart deserve attention 

 in this connection. He shows that nicotine paralyzes the nerve cells, 

 and not the nerve endings in the heart, while muscarin will stop the 

 heart after the application of the nicotin, and that atropin " will put an 



'Cf. the researches which follow, by Langley. 



