Feb. 1902.] BOTANICAL SOCIETY OF EDINBUKGIl 175 



Eegarding the inhibition of intestinal muscle through 

 splanchnic stimulation as the establishment of the phase 

 of anabolism, we have anabolic inertia expressed in the 

 persistence of the state of relaxation after the inhibitory 

 stimulus has been withdrawn. This post-stimulant relaxa- 

 tion may last for 25". Similarly, after the withdrawal of 

 stimuli in cardiac inhibition, there is a (post-stimulant) 

 " latent period " before the heart resumes beating, due to 

 the anabolic inertia of cardiac protoplasm. The latent 

 period that exists before secreto-motor effects in glands 

 appear, is the expression of anabolic inertia in glandular 

 protoplasm : in stimulation of vagal pancreatic secreto- 

 motor fibres, it is as long as 1 5" to 3'. Verworn ^ tells 

 us that " the motion of cilia does not begin at the exact 

 moment at which the light strikes them," but only after 

 a " latent period " of one to two seconds — this is anabolic 

 inertia. 



More especially expressed under the category of rhythm, 

 we have all those cases of intermittent discharges or series 

 of effects from an (apparently) single stimulus, e.g. Hitter's 

 tetanus, Wundt's tetanus, and the strychnine tetanus. 

 These are rhythmic expressions of inertia, comparable 

 to the oscillations of the jelly consequent on a single 

 tap given to it. Functional inertia may express itself 

 in the maintenance of a certain rhythm of discharge of 

 impulses, as has been brought out by Professors Horsley 

 and Schafer in their experiments upon the normal rate of 

 discharge of cells of the spinal cord. They showed that 

 whatever was the rhythm of stimulation, provided it was 

 ten per second or more, artificially imposed upon the 

 nerve-tracts proximal to the cells, the rhythm of discharge 

 was always ten per second, not more. The protoplasm of 

 these spinal cord cells has its own phase of physiological 

 insusceptibility, its " refractory period," and no artificial 

 rate of stimulation will accelerate the rhythm (provided 

 the stimulation be below a certain intensity) — this is 

 functional inertia. The anabolic inertia of the cells of 

 the reflex "centres" of the spinal cord must be the 

 principle underlying the insusceptibility to single stimuli, 

 and the necessity for " summation " of stimuli before the 

 " General Physiology,"' p. 401. Macmillan : Londou, 1899. 



