1883 | Organic Physics. 141 
tory influence is that of photographic compounds. , These can be 
made so exquisitely sensitive that the faintest touch of the rays 
of light produces instantaneous chemical change. The responses 
of protoplasm to touch are even less delicate than those of some 
of these inorganic substances. 
We have considerable warrant for ascribing protoplasmic action 
to a like result of contact influence. It never takes place except 
oxygen be present. Probably it is necessary that oxygen should 
permeate, or be stored up in the protoplasmic mass, the molecules 
of oxygen and protoplasm being intimately mixed, like those of 
hydrogen and chlorine in the mixture above referred to. Andin 
both cases the commingled molecules seem to resist the energy 
of chemical affinity until a vibratory motion, originating without, 
is sent through the mass, and flings them into closer contiguity. 
The mixture of oxygen and protoplasm, however, appears much 
more sensitive than that of hydrogen and chlorine. In the latter 
case only the vigorous vibrations of sunlight seem sufficient to 
induce combination. In the former case every source of vibra- 
tion yields this effect, as might be expected from the high insta- 
bility of protoplasm molecules, and the strong affinity of some of 
their elements for oxygen. 
Various sources of vibratory influence exist in nature. First 
are the radiant vibrations of sound, heat, light and electricity, to 
all of which protoplasm seems susceptible. Next come several 
forms of direct contact, as of gaseous, liquid and solid substance, 
each of which may produce a vibratory thrill, Then there are 
the vibrations of inflowing or outflowing temperature. Perhaps 
still other sources of vibration exist, and to all alike protoplasm 
seems susceptible. Every vibration, even the slightest, from 
Whatever source, which enters into and acts upon protoplasm, ap- 
parently induces combination with oxygen (if this element be 
present), with a consequent freeing of motor energy, and produc- 
tion of some physical change. 
3 Yet, as it would prove destructive to all high animal life should 
the protoplasin of the cells be exposed to every vibratory thrill of 
outer nature, and forced to respond thereto, the body generally is 
Covered with a protective coating, through which only the more 
vigorous vibrations produced by contact pressure and heat energy 
can pass, and is provided with nerve terminations specially adapted 
— receive | Toos of such character. There are only two 
