(i7) 
of organic life, as starch, C6 IIio O5, grape-sugar, C6 H12 06 
cane-sugar, C6 II22 Oil ; and finally, the most highly complex 
of the organic compounds, as cerebrin, C57 ITi 10 N2 O25 (a 
substance found in the brain), and protagon, C160 H308 
PO35 (a constituent of nerves). 
IIow the transition from the non-living to the living was first 
effected, we do not know. Whether life first appeared in dead, 
insensate, matter by a creative fiat, or whether it began to dawn 
as the result of increasing complexity of chemical combination, 
the my stew is alike inexplicable. Let us, then, not pause here, 
but go on to trace and depict the scheme of life’s origin and de¬ 
velopment as we know it to-day. 
Animals and plants are made from a material which, in its 
essential character, is common to them both. This material from 
which they are both built up, this physical basis of life, is known 
as protoplasm.* Protoplasm, then, is the simplest form of living 
matter: as the atom is the unit in chemistry, so protoplasm is the 
unit in the world of life, and the most complex of living things 
is but an aggregation of protoplasm. I should now impress 
upon you the properties of protoplasm, for the highest forms of 
vegetable and animal life have no other properties than these. 
The most marked characteristics are as follows: Protoplasm has 
the property of taking up, and making part of itself, other living 
or non-living matter, whereby it grows ; on reaching its maturity, 
it is able to reproduce one or more individuals like itself; it then 
undergoes a retrograde transformation, its activity diminishes, 
and it dies. This series of changes through which each indi¬ 
vidual mass of living matter must pass—growth, reproduction, 
and death—is most distinctive. A second property of living 
matter is its irritability. If anything comes into contact with 
protoplasm, there is an instant change of its latent into actual 
energy, expressed by motion, or by heat, light, or electricity. 
Another peculiar function is the power of automatic motion. 
If we observe a mass of protoplasm under the microscope, we 
shall see an almost constant motion in it—a gliding or outstretching 
of some portion of its substance. A fourth characteristic is the 
extremely complex chemical composition of protoplasm. 
♦Fig. 4. 
