INTRODUCTION, 3 



obtains his insight, according to whether he gathers his 

 knowledge through immediate observation, or after a 

 previous dissection with scalpel and scissors, or by use of 

 the microscope. Therefore it is not justifiable to place 

 Morphology and Anatomy over against one another, and 

 to ascribe to the former the description of only the external, 

 and to the latter of only the internal parts. The distinc- 

 tion is not logically correct, since the kind of knowledge 

 and the mental processes of the research are the same in 

 both cases. The distinction, too, is unnatural, since in 

 many instances organs which in some cases lie in the 

 interior of the body, and require for their knowledge an 

 anatomical preparation, belong in other cases to the sur- 

 face of the body, and are accessible for direct description. 

 Further, the internal parts of many animals on account of 

 their transparency can be studied without dissection. 



Comparative Anatomy. For Morphology, as for every 

 science, the proposition is true that the mere accumu- 

 lation of observed facts is not sufficient to give the subject 

 the character of a science ; an additional mental elabora- 

 tion of this material is necessary. Such a result is reached 

 through comparisons of anatomical discoveries. The mor- 

 phologist compares animals with each other according to 

 their structure, in order to ascertain what parts of the 

 organization recur everywhere, what only within narrow 

 limits, possibly restricted to the representatives of a single 

 species. He thereby gains a double advantage: (i) an 

 insight into the relationships of animals, and hence the 

 foundation for a Natural System ; (2) the evidence of a 

 law which governs organisms. The single organism is not 

 a structure which has arisen independently and which is 

 hence by itself intelligible : it stands rather in a legitimate 

 dependent relation to the other branches of the animal 

 kingdom. We can only understand its structure when 

 we compare it with the closely and the more distantly 

 related animals, e.g., when we compare man with the 

 other vertebrates and with many lower invertebrated 

 forms. Here we have to consider one of the most mys- 



