INTRODUCTION. 35 



to observation, namely, their form. Microscopical anatomy is concerned 

 with the understanding of the microscopic forms, and with the laws of 

 their structure and development, not with any general doctrine of the 

 elementary parts. Composition and function are only involved, so far 

 as they relate to the origin of forms and to their variety. Whatever 

 else respecting the activity of the perfect elements and their chemical 

 relations is to be found in Histology, is there either on practical grounds 

 in order to give some useful application of the morphological conditions, 

 or to complete them ; or from its intimate alliance with the subject, it is 

 added only because physiology proper does not afford a due place for 

 the functions of the elementary parts. 



If Histology is to attain the rank of a science, its first need is to 

 have as broad and certain an objective basis as possible. To this end 

 the minuter structural characters of animal organisms are to be examined 

 on all sides, and not only in fully formed structures, but in all the 

 earlier periods from their first development. When the morphological 

 elements have been perfectly made out, the next object is to discover 

 the laws according to which they arise, wherein one must not fail to 

 have regard also to their relations of composition and function. In dis- 

 covering these laws, here as in the experimental sciences generally, 

 continual observation separates more and more, among the collective 

 mass of scattered facts and observations, the occasional from the con- 

 stant, the accidental from the essential, till at last a series of more and 

 more general expressions of the facts arises, from which, in the end, 

 mathematical expressions or formulae proceed, and thus the laws are 

 enunciated. 



If we inquire how far Histology has satisfied these requirements, 

 and what are its prospects in the immediate future, the answer must be 

 a modest one. Not only does it not possess a single law, but the 

 materials at hand from which such should be deduced, are as yet re- 

 latively so scanty, that not even any considerable number of general 

 propositions appear well founded. Not to speak of a complete know- 

 ledge of the minuter structure of animals in general, we are not ac- 

 quainted with the structure of a single creature throughout, not even 

 of man, although he has been so frequently the object of investigation, 

 and therefore it has hitherto been impossible to bring the science 

 essentially any nearer its goal. It would, however, be unjust to over- 

 look and depreciate what we do possess ; and it may at any rate be said 

 that we have acquired a rich store of facts and a few more trustworthy 

 general propositions. To indicate only the more important of the for- 

 mer, it may be mentioned, that we have a very sufficient acquaintance 

 with the perfect elementary parts of the higher animals, and that we 

 also understand their development, with the exception of the elastic 

 tissue, and of the elements of the teeth and bones. The mode in which 



