21 
of constitution. It is almost superfluous to remark here, that the primal 
constitution of living matter as compared with that of inorganic substances, 
is characterised by differences which separate the two so widely, that we 
gain little by calling the reaction of an organic substance "vital," for we 
are forced to couple with this " vitality" the fact, that its manifestation 
appears inseparable from that of the observed properties of the matter of 
which living beings are composed. 
That organic matter is derived from inorganic matter, so put together 
as to occasion the manifestation of properties unobserved in dead matter, 
cannot at the present day be any longer disputed. But, again, those pro- 
perties of matter, the manifestation of which constitute our only evidence 
of vitality, are known to us. only as phenomena induced by the operation 
of external agents on the substance under examination. The "property" 
is a potential quality of matter, and its manifestation is due to the reaction 
of the substance, not of the agent influencing it. That such reaction 
should differ in different substances — or, in other words, that different 
properties should be manifested in the several protein compounds, (e. g. 
albumen, fibrin, casein, &c. — protein compounds of the first class), would 
lead us to infer that, as their chemical composition is not perceptibly 
altered, the physical disposition or atomic arrangement of their elements 
may be changed. 
Now, the protoplasm of tho lowest animals may be chemically isomeric, 
just as the protein compounds are, yet capable of different reactions, 
according as external agents affect them, and as their atomic elements are 
differently arranged. And if our protoplasm consist of more than one 
protein substance, we may fairly suppose that the "properties" of the 
compound protoplasm will differ as one or other constituent predominates. 
In the chemistry of organic substances, a process of re -arrangement by 
substitution of elements, accompanied by change of properties, is well- 
known, and by some such process, the protoplasm of various animals may 
become possessed of different properties, which would form the starting 
point of future differentiation and evolution. The influence of the surround- 
ing cosmic media must, in this case, be all important on the behaviour of 
the protoplasm, for the variable reaction will depend on diversity of 
stimulus as well as on diversity of organic constitution. 
What, then, are we to say to the vital force doctrine? Simply this, 
that it is an expression of the fact that living matter reacts in a determi- 
nate direction when influenced by certain agents. The property of living 
matter thus to react is what we call vitality ; but whether it manifests 
