1901-2.] Functional Inertia, a Property of Protoplasm. 197 
under category of latent period, we have the latent period of 
stimulation of the cardiac vagus, the relatively long time (18 
seconds) before stimulation of splanchnic nerve is followed by inhibi- 
tion of intestinal peristalsis, the time during which the frog-heart 
will beat at accelerated rate (30 seconds) after the withdrawal of 
accelerating stimulus. 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 duration of the ‘ latency ’ or 
non-response being longer or shorter according to the function and 
kind of protoplasm considered, being in some cases of vegetable 
protoplasm an hour or more. It is thus the opposite property to 
‘irritability ’ or affectability. In fact, functional inertia as non- 
response is the property underlying physiological insusceptibility 
it is thus the functional counterpart of affectability. 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. Just as non-living matter 
cannot be instantaneously caused to change its state, neither can 
bioplasm ; by the inertia of its mass or its motion, c inert ’ matter 
tends to remain in the status quo ante ; by the inertia of its 
livingness — in relative rest or in relative activity — bioplasm tends 
to remain in its metabolic status quo ante . 
As general examples of katabolic inertia, there is that large 
class embracing all cases of local life of organs, tissues or cells after 
somatic death, the post-mortem expression of the functional inertia 
of katabolism, e.g., the muscle and nerve of the familiar nerve-muscle 
preparation which still ‘ act ’ though removed from their nutrient 
lymph, the excised (isolated) bloodless frog-heart beating on a 
glass plate for hours after the death of the animal, the excised 
medullated nerves still giving evidence of conductivity for many 
hours after isolation, the vivisected non-nucleated portion of 
Lacry maria olor and other Protista,* the ciliated epithelium from 
frog living for days as an isolated patch, and the cilium detached 
from the cell exhibiting movements ‘till it perishes.’ In this class 
I do not include the cases of organs surviving by reason of perfused 
defibrinated blood, for here their metabolism is being constantly 
supported by nourishment applied under artificial conditions, and 
* Verworn, General Physiology, p. 570. London, 1899. 
