714 PHYSIOLOaY IN RELATION TO 



of its value is furnislied us by the fact, that in Edinburgh as in 

 Germany a dissertation on some subject of Comparative Anatomy 

 is often accepted as a thesis for the degree of Doctor in Medicine. 

 By such a regulation we have the obvious fact recognised, that the 

 same sort of skill in the employment of methods, the same fami- 

 liarity with organs, tissues, and functions, the same reasoning 

 powers, are employed in investigating the problems of life where- 

 soever existing. The second aphorism of the ' Novum Organon ' 

 applies to the one as to the other line of investigation, that of 

 Human, and that of Brute Biology : — Instrumentis et auxiliis res 

 perjicitur ; and alike in both, nee manus nuda nee intellectus sihi per- 

 missus multum valet. Comparative Anatomy, finally, besides thus 

 benefiting the public firstly, and the profession secondly, is of use 

 to Human Biology and Medicine, as such, inasmuch as it casts so 

 much light upon the problems which the more highly evolved 

 organs, functions, and other relations of our own species render in 

 a much higher, and, indeed, sometimes in the highest degree, 

 difficult or impossible to investigate. Answers to what are riddles 

 in Human Anatomy and Physiology are often to be found given in 

 very simple language in the structures and functions of the lower 

 and lowest animals. Of such hints furnished by the brute creation 

 towards the proper solution of certain problems which concern each 

 and all of us in dealing with our own species, I will herewith, by 

 your permission, give a few. Of the use of rest towards the repair 

 of injuries I presume there is little doubt, but the best established 

 teaching is all the better for the support of a few concrete ex- 

 amples. Now, in what animals do we find the greatest capacity 

 for repair of injuries, and for the reproduction of lost parts and 

 limbs? Precisely in those in which the whole of life is carried on 

 at the lowest rate, and in the nearest approximation to rest which 

 is compatible with animality,-^in those animals, to wit, which 

 breathe water, and have but its scanty percentage of dissolved 

 oxygen to sustain their animal functions. The metamorphoses 

 which an animal may have undergone, or may have to undergo, 

 have very little directly to do with its power of recovery from injury, 

 or of regenerating a lost limb. No animals go through more com- 

 plex metamorphoses than do many of the Crustacea, and nearly all 

 the Echinodermata ; yet assuredly no other class has a larger 

 capacity for the reproduction of lost fragments of their bodies. 



