6l2 'Journal of Comparative Neurology and Psychology. 



adapted to the function of that neurone ? Is it graded in propor- 

 tion to the stimulus received? In general, no; and it is probable 

 that this would by no means always result in adaptation or in 

 successful reflex action. Subliminal stimuli do not cause dis- 

 charge of the neurone unless summated. Adequate stimuli pro- 

 duce responses of normal strength. Increased strength of stimu- 

 lus in reflexes produces increased response only or chiefly by 

 involving a larger number of neurones. Reference is made here 

 to Sherrington's discussion of the subject of grading of intensity 

 in chapter iii of his book on the Integrative Action of the Nervous 

 System. In general, a neurone in normal and unfatigued condition 

 is able to perform about a certain amount of work and that normal 

 response it gives to any stimulus within a considerable range of 

 intensity. 



Is the strength of impulse determined by the size or structure of 

 the cell-body or dendrites .? It has usually been thought that some 

 relation exists between the size of a neurone and its activity or the 

 number of tissue elements with which it is related. The nature 

 of this relationship has been very obscure. The writer is inclined 

 to think that the size of the cell-body and dendrites has to do with 

 the nutritive and the receptive functions of the neurone rather 

 than with its effx?ctive functions. The volume of the cell-body and 

 dendrites and the ramifications of the latter certainly are impor- 

 tant factors in the nutrition of the neurone. Also, those neurones 

 whose axones are long often have large cell-bodies, e.g., motor 

 neurones generally. This is doubtless because the nutrition of the 

 whole neurone is, as is known, in some way dependent upon the 

 nucleus of the cell. On the other hand, it is somewhat commonly 

 true that those neurones which have large and richly branched 

 dendrites may receive impulses from a large number of fibers and 

 perhaps from fibers from various sources. Examples of this are, 

 motor neurones, Purkinje neurones in the cerebellum, pyramidal 

 cells of the cerebral cortex, etc. Examples of neurones whose 

 dendrites are obviously adapted to the reception of impulses from 

 a small number or a definite kind of fibers are: granule cells in 

 the cerebellum, neurones in the tectum opticum related to the 

 optic tract fibers, mitral cells of the olfactory bulb, etc. It is, 

 indeed, difficult to see how the strength of the impulse delivered 

 at the end of the axone could be determined by anything in the 

 cell-body and dendrites without ascribing to the axone the func- 



