THE PHYSIOLOGY OF THE NEURON. 



Truly, to find out the properties of a single neuron would be 

 a task appalling enough; but, when we remember that of the 

 millions of neurons in one individual perhaps no two are just 

 alike, the quest would seem hopeless. But instead of burying 

 ourselves in pessimistic reflections, or being discouraged by 

 what is at present unattainable, by what may perhaps forever 

 remain to us unknowable, we may profitably turn to the con- 

 sideration of some of the points which lie more within our 

 ken. One point, self-evident enough when one's attention is 

 directed to it, but which often appears to have been overlooked 

 in connection with the neurons, is the unremitting character 

 of their activity. With a metabolism as complicated as that 

 occurring within the nerve-units it is inconceivable that there 

 can be any period in which alterations in chemical structure, 

 and consequently energy transformation, are not going on. 

 From moment to moment, throughout all the hours of the 

 day and night, analytical and synthetic processes are taking 

 place, associated with the alterations in physical forces which 

 necessarily accompany these changes. In common with every- 

 thing that lives, the neurons know no absolute repose. As I 

 have said, in speaking of their metabolism, periods of extrava- 

 gant activity may alternate with periods of more -economic 

 change, but total rest is inconsonant with continuance of ex- 

 istence. We are forced to believe that what we ordinarily 

 speak of as the passage of a nerve-impulse represents, as it 

 were, a stormy process in the nerve-fiber, and that just as absence 

 of a storm does not mean absence of weather, there are in all 

 probability minor alterations currents, if you will passing 

 to or fro or passing to and fro in a given nerve-fiber in the in- 

 tervals between the more violent excitations." 



The words that we have italicized will doubtless recall 

 some of the more prominent features previously emphasized 

 in respect to the relative nervous processes involved in the 

 functions of the various organs reviewed. We have termed 

 "passive" that form of energy continuously transmitted to tis- 

 sues and vessel-walls. A quiet and steady flow of blood into 

 the cellular structures, sustained by the tonic contraction of 

 the arteries, and a stream of nervous impulses to the tissues 

 coinciding in rhythm, perhaps, with that sent to the vessels, 



