

THE 



ORIGIN OF VERTEBRATES 



INTRODUCTION 



In former days it was possible for a man like Johannes Muller 

 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 



B 



