LIFE. 13 
The vital functions of organisms are :— 
Primary. — 1. Alimentation. 
2. Movement. 
3. Sensation. 
4. Excretion (and Secretion). 
Secondary.—1. Growth. 
2. Reproduction. 
It cannot be too much insisted upon that these vital 
functions are all exhibited by all living organisms from 
highest to lowest. 
If the secret of vital phenomena ever be revealed to the 
future scientific investigator, the steps from 4ewéa to man 
will appear as a mere nothing compared to the immeasurable 
difference between living protoplasm and its non-living con- 
stituent proteids. 
We know life only by its effects, not in itself, and 
the student should ever bear in mind that just as the 
physicist has to assume the fundamental conceptions of 
matter and motion, so the zoologist, the biologist and. the 
physiologist have to start with the assumption of life and its 
vital phenomena. The attempt to explain these premises 
in each case is mere speculation. 
