THE 
ORIGIN OF VERTEBRATES 
INTRODUCTION 
4 
In former days it was possible for a man like Johannes Miiller 
to be a leader both in physiology and in comparative anatomy. 
Nowadays all scientific knowledge has increased so largely that 
specialization is inevitable, and every investigator is confined more 
and more not only to one department of science, but as a rule to 
one small portion of that department. In the case of such cognate 
sciences as physiology and comparative anatomy this limiting of the 
scope of view is especially deleterious, for zoology without physiology 
is dead, and physiology in many of its departments without com- 
parative anatomy can advance but little. Then, again, the too 
exclusive study of one subject always tends to force the mind into 
a special groove—into a line of thought so deeply tinged with the 
prevalent teaching of the subject, that any suggestions which arise 
contrary to such teaching are apt to be dismissed at once as heretical 
and not worthy of further thought; whereas the same suggestion 
arising in the mind of one outside this particular line of thought 
may give rise to new and valuable scientific discoveries. 
Nothing but good can, in my opinion, result from the incursion 
of the non-specialist into the realm of the specialist, provided that 
the former is in earnest. Over and over again the chemist has 
given valuable help to the physicist, and the physicist to the 
chemist, so closely allied are the two subjects; so also is it with 
physiology and anatomy, the two subjects are so interdependent 
that a worker in the one may give valuable aid towards the solution 
of some large problem which is the special territory of the other. 
It has been a matter of surprise to many how it came about that 
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