FUNCTIONAL INERTIA AS LATENT PERIODS, &c. 39 



in " inspiratory tetanus" in a tremor of about 3 or 

 4 a second periodicity (cf. Fig. 9). Now superior 

 limits are inertial. 



I am far from saying that Pfliiger's account could 

 not be brought into line with my views provided 

 the inertia of living molecules be granted : I would 

 then prefer " predominant katabolism " to " excita- 

 tory processes " and " predominant anabolism " to 

 " inhibitory processes." Further, I think, that 

 :< normal metabolic process " should not itself be 

 identified with stimulus, since the former is the state 

 of the material on which the latter operates. Thus 

 I believe that for the maintenance of the normal 

 respiratory rhythm both the fundamental properties 

 are responsible, affectability on the side of response, 

 and functional inertia on the side of disregard of 

 stimuli, the existence of limits, and inherence of 

 spontaneity in rhythm. The physical analogy in the 

 case of rhythms is the pendulum or the rocking- 

 stone or the person on the swing ; once started they 

 continue in their own particular periods, alternately 

 exhibiting the inertia of position and that of motion. 

 I have the sanction of no less a physiologist 

 than Professor Angelo Mosso for the attributing 

 of inertia to the respiratory mechanism. Thus, 

 speaking of the alterations in respiratory rhythm 

 consequent on warming and cooling animals he 

 writes * : " There is, therefore, a degree of inertia in 

 this apparatus for reducing the temperature by means 

 of the respiration, for an animal placed in a much 



* A. Mosso " Fatigue," translation of " La Fatica," p. 114. 



