FUNCTIONAL INERTIA AS LATENT PERIODS, &c. 31 



tion into it may be profitably made especially as 

 its experimental physiology has been pretty well 

 worked out. 



I shall first quote the view of Professor Starling,* 

 in which an account of the rhythmicality of the 

 centre is given in which it is desired to do without 

 the conception of inertia. " The stimulus derived 

 from the blood is, under normal conditions of 

 respiration, constant. The stimulus derived from 

 the afferent nerves is subject to rhythmical variation 

 and . . . this variation is of considerable importance 

 for the maintenance of the normal respiratory 

 rhythm. The centre can, however, go on discharging 

 rhythmically in the absence of any afferent rhythmic 

 stimulation" (double vagotomy is here alluded to). 

 ' We have, therefore, to discuss how the centre is 

 able to respond to a constant stimulus with a rhythmic 

 discharge. The simplest explanation of this process, 

 if explanation it can be called, is to say that it is 

 a property of the nerve-cells as of the muscle- 

 cells of the heart to respond to a constant stimulus 

 by a series of rhythmic discharges. Pfluger con- 

 siders that the molecular processes in a living cell 

 may be divided into two sets those which tend to 

 produce a discharge of energy and those which tend to 

 prevent a discharge. In more modern terms we might 

 speak of these two processes as katabolic or dissimila- 

 tive and as anabolic or assimilative. In a condition 

 of rest these processes balance one another exactly. 



* Starling, in " Text-book of Physiology." Edited by Schafer, 

 Vol. ii. p. 291. (Pentland.) 



