Feb. 1902.] BOTANICAL SOCIETY OF KDINBURGII 173 



elapse between the instant of the application of the stimnlus 

 and the consequent cardiac inhibition. The heart, in other 

 words, gives no "outward and visible sign" of the impending 

 change of condition during, it may be, two beats — the time- 

 expression of the katabolic inertia of cardiac protoplasm. 

 It is shorter but demonstrable in the mammalian heart. 

 Again, it is in virtue of the katabolic inertia of nonstriated 

 muscle that there elapses the relatively very long time 

 (latent period) of IS'' before stimulation of the splanchnic 

 nerve is followed by inhibition of the intestinal movements, 

 i.e. induces the anabolic phase. Similarly, the phase of 

 predominating katabolism having been induced, e.g. in 

 cardiac acceleration, it will be maintained for 30'' (frog- 

 heart) after the withdrawal of the accelerating stimulus, 

 in virtue of the cardiac katabolic inertia. Thus, as 

 exhibited under the time category, functional inertia is 

 that property of protoplasm in virtue of which it does not 

 respond to a stimulus (the time of non-response or latency 

 being longer or shorter according to the tissue and function, 

 in the case of vegetable protoplasm relatively very long — 

 an hour or more), and is thus the opposite property to 

 affectability or irritability. Viewed under the category of 

 non-response itself, functional inertia is the property under- 

 lying physiological insusceptibility, " refractory period " 

 and allied states ; it is thus the functional counterpart of 

 irritability. It is by reason of the property of irritability 

 that living matter responds to stimuli, but it is in virtue 

 of its other property of functional inertia that it does not 

 do so instantaneously. It is by reason of its affectability 

 that the quiescent heart performs a systole on stimulation; 

 it is by reason of its functional inertia that it performs a 

 maximal systole — the "all or nothing" action, as it has 

 been called, and in virtue of which the heart cannot be 

 tetanised. Just as dead matter cannot be instantaneously 

 caused to change its state, neither can bioplasm ; by the 

 inertia of its mass, or of its motion, " dead " matter tends to 

 remain in the status quo ante ; by the inertia of its living- 

 ness (in relative rest or in relative activity) protoplasm 

 tends to remain in its (functional) status quo ante. 



Passins; to cases where there is a conscious correlate, we 

 have, in the positive after-sensation, a good example of 



