Meyer, Data of Modeim Neurology. 295 



eral segments of the neural tube, and towards many types of 

 cells. Among them are cells connected with various groups of 

 muscles (various kinds of efferent neurones, see p. 135), and 

 intermediate cells, segmental or supra-segmental (see p. 141, 

 etc.). Each cell is in a definite state of nutrition and by this 

 and its connections represents the sum-total of its previous life ; 

 it is, as it were, ' attuned to ' a certain range of reaction, will 

 react to certain stimuli only with a characteristic action, while 

 other influences would leave it passive. Among the many cells 

 which are reached by the afferent nerve only those will react 

 which are ' attuned to ' a definite impulse and give the ade- 

 quate reaction. Under no circumstance is it possible to stim- 

 ulate ONE efferent cell, but a reflex arc consists always of (i) an 

 afferent (at least one), and (2) many efferent neurones of one 

 group of coordinated muscles and (3) the necessary number of 

 intermediate cells. If a certain stimulus is complicated, the 

 state of excitation of the afferent neurone may be of such a char- 

 acter as not to ' appeal ' directly to the segmctital efferent neu- 

 rones ; cerebellar and cerebral afferent neurones however may re- 

 spond to that form, and the functional groups of cerebellar and 

 cerebral efferent neurones respond to the excitation received in 

 the only way in which they can respond, through specially ' at- 

 tuned ' .yr^wrw/^/ efferent neurones. If the reaction is complica- 

 ted we might call it automatic, following the customary con- 

 cepts without subscribing to the uncritically accepted dogma 

 that whatever is ' automatic ' must once, have been voluntary 

 and therefore conscious. Or the stimulus may produce such a 

 state of function in the cerebral afferent cells that ' psychical ' 

 elements are the only neurones which take it up or respond to 

 it, and from this the state of activity may, or may not, spread on 

 to definite groups of cerebral efferent neurones, reaching either 

 the motor apparatus of expression in the case of simple thought 

 and speech, or other groups of segmental efferent neurones 

 (voluntary and vaso-motor action.) In this way indefinite 

 numbers of selections can be obtained. And we repeat, that 

 these unconscious or conscious reactions presuppose three types 

 of conditions, (i) A special stimulation of afferent neurones, 



