196 Proceedings of Royal Society of Edinburgh. [sess. 
Functional Inertia, a Property of Protoplasm. By David 
Fraser Harris, M.D., B.Sc. (Lond.), Lecturer on Physi- 
ology and Histology, University of St Andrews., 
(Read February 3, 1902.) 
[Abstract.) 
1 Dead ’ matter has two forms of inertia — that of rest (mass), and 
that of motion (momentum) — and it seems to me that living 
matter possesses a property, not hitherto recognised as such, which 
might he called functional inertia, or metabolic inertia of proto- 
plasm whether animal or vegetable. It is owing to the inertia of 
matter at rest that the heavy gate, swung even on almost friction- 
less hinges, cannot he instantaneously set in motion ; and when it 
has been set swinging, it is owing to its inertia of motion 
(momentum) that it continues to swing for some time after we 
have ceased to push it. By functional inertia of protoplasm I 
mean the power or property of protoplasm to remain in the meta- 
bolic status quo ante ; if resting — anabolising — to remain doing so, 
even after the reception of a stimulus tending to bring about the 
opposite metabolic state, this might be called anabolic inertia ; if 
active — katabolising — to remain so even after the reception of a 
stimulus tending to induce anabolism, or after the cessation of the 
stimulus that elicited the activity — katabolic inertia or functional 
momentum. Functional inertia is the power or property which 
bioplasm has of maintaining its functional status quo for a longer 
or shorter time according to the function considered ; it is that 
power of continuing to exhibit the particular phenomena it has 
been exhibiting even after the death of the organism of which it 
is a constituent. The inertia of livingness expresses itself under 
several more or less distinct modes or categories — viz., ‘latent 
period ’ if we study time-relation to stimulus, the bio-chemical, or 
pre-eminently the metabolic, refractory period (physiological 
insusceptibility) if we study affectability (‘irritability’), rhythm 
if we study alternation of metabolic phase, and finally the psychical 
if we study conscious correlates. As examples of katabolic inertia 
