234 Protoplasmic Dynamics. [ April, 
combination of some of the fundamental operations, whether 
physiological, mechanical, physical or chemical, as they exist in 
one continuous process pertaining to protoplasmic things, is my 
present undertaking. 
I.—Protoplasm masses and molecules, or their parts, may be 
set in motion by the impact or attraction of active masses or 
molecules or atoms, without or within. 
The agitations thus imparting themselves are various and, be- 
cause communicative, may be regarded as excitants or incitive 
actions, already called stimuli or irritants. These include mass- 
motions, such as pressure, blows and friction; molecular motions, 
chiefly vibratory or oscillatory, as sound, electricity, light and 
heat; also atomic motions; and with these are the attractions be- 
longing to these divisions of matter respectively, as gravitation 
(weight), cohesion and adhesion (osmotic, diffusive, capillary, &c.), 
and finally chemism. Important sources of some of these are the 
chemical reactions of oxygen, water, and the ingested nutriment, 
constituents with each other and with the protoplasm elements ; 
others proceed from contact with the active materials of the envi- 
ronment; while the sun also continually contributes. ; 
II.—All the above disturbing forces tend to cause the displace- 
ment, mutilation, fission or decomposition of molecules or their 
parts, which is especially easily accomplishable against weak com- 
binations of ponderous, complex molecules, such as distinguish 
organic bodies. 
I1I.—When molecules or their parts are thus separated, their 
combining powers are set free, and this liberation of attractional 
forces will be sustained by the continued operation of the original 
displacement forces, or may become, to some extent, self-propa- 
gated after their cessation by the disturbance (heat, &c.) resulting 
from recombination; for the impact of every union manifests itself 
in new disturbing fortá, which, in turn, may disband other attrac- 
tions, from which further combinations follow. 
An illustration of this self-sustained process is common in every — 5 
form of combustion. The little heat-agitation applied to a very 
small part of the mass to be consumed, frees attractions there, 
which satisfy themselves by uniting with the ever-present oxygen, 
thereby generating more heat, sufficient to renew itself by indu- — 
cing further chemical reaction so long as fed with the materiak for 
consumption. 
