JOHANNES MULLER 523 



ality, as it was manifested in the home and among the ranks of his 

 students and associates. 



In the estimation of a man's prominence it is hardly necessary to 

 remark that the importance which he may assume is always a relative 

 quantity. It is first roughly drawn from a direct comparison of this 

 individual with other individual workers. It is then tempered, as we 

 may say, by a consideration of the relation of the individual activities 

 to the whole field of knowledge existent at that time. There may be 

 great physiologists, great morphologists and great systematists, but the 

 criterion invariably to be used to determine the highest rank must 

 ever be that comprehensive vision which, as Verworn remarks, is able 

 to grasp in a single Weltanschauung, the whole breadth and depth of 

 natural scientific inquiry — that comprehensive analytic and synthetic 

 quality of mind which brings isolated unities of fact into concrete 

 principles. It is from this point of view, and by these standards that 

 we must judge the extent and quality of the work of Johannes Miiller : 

 first examine into the relation of his activities to the field of natural 

 science of his day; and, secondly, ascertain the relative value of his 

 work when compared with the labors of other men whom posterity has 

 been accustomed to hold as leaders in the rank and file of natural sci- 

 entists. And yet, before we can fully understand — much less appre- 

 ciate — the intrinsic worth of any phase of Mullens many-sided activity, 

 we must first take time to examine briefly the condition of the biolog- 

 ical science just previous to the period of Miiller's greatest work. 



We have already in the course of our discussion made mention of 

 the scope and value of Haller's work in physiology; yet we may be 

 pardoned, perhaps, if, in the present connection, we again make refer- 

 ence to some of the more important characteristics of his period, 

 which extended from 1708 to 1777, and closed something over half a 

 century before Miiller's began. 



As Galen, in the second century, had shown his recognition of the 

 practical value of physiological data and had laid as a basis of medi- 

 cine, the practical knowledge of vital phenomena; as Harvey, by his 

 brilliant discovery of the circulation of the blood, temporarily revived, 

 after a sleep of thirteen centuries, the exact experimental method in 

 physiology; and after many other investigators had made important, 

 though isolated, contributions to the budget of physiology, we find 

 Haller bringing together the extensive mass of facts and theories and 

 establishing thereby physiology as an independent science which should 

 pursue not only practical lines for the aid to medicine, but also under- 

 take theoretical aims for their own merit. We find many theories and 

 speculations in the air during the period from 1750 to 1830, the latter 

 date marking the beginning of the period of Miiller's greatest activity. 

 As a result of the microscopical observations made in last part of 

 the seventeenth century on the development of the ovum, the theory 



