248 THE CELL-THEORY 



have a histological development as well as a histological anatomy. 

 Leuwenhoek and the majority of his successors had enough to do 

 in making out the " histoi-kam cognitionem" the simple anatomy of 

 the tissues ; it tasked all their powers to arrive at a clear statement of 

 the " theorem',' while it is the great merit of Schleiden and Schwann 

 that they sought to arrive at an " anatomia rationalis" and to furnish 

 the " demonstration of the theorem." The old method of investi- 

 gation had been carried as far as it would go, and they applied the 

 only other «-hich remained, and made it familiar to the general mind. 

 Turn to any of Schleiden's works, and we find the logical acuteness, 

 and the vituperative sarcasm, which he wields with equal force, 

 employed in urging the study of development as the one thing 

 needful for scientific botany. x*\nd Schwann's entire essay testifies to 

 what he expressly tells the reader, that his investigations are distin- 

 guished from all others by being based upon the study of development. 

 Let one citation suffice : — " The theory of the present investigation 

 was, therefore, to show . . that there exists a common principle of 

 development for all the elementary parts of the organism." (Schwann, 

 pp. 193—196.) 



Intending as we do to venture upon a critical examination of the 

 absolute value of Schleiden's and Sch^'ann's contributions to biological 

 science, which may lead us to conclusions not ordinarily admitted, we 

 have been particularly desirous to estimate fairly the position which 

 they occupy in its history, and the influence which their labours have 

 had upon its progress — which is a widely different matter — for, in 

 attempting to weigh the labours of others, we should be in danger of 

 committing great injustice, if we did not carefully bear in mind that 

 paradoxical as it may seem, the value of a theory and its truth, are 

 by no means commensurate. In so complex a science as that which 

 relates to living beings, accurate and diligent empirical observation, 

 though the best of things as far as it goes, will not take us very far ; 

 and the mere accumulation of facts without generalization and classi- 

 fication is as great an error intellectually, as, hygienically, would be 

 the attempt to strengthen by accumulating nourishment without due 

 attention to the prima; vix, the result in each case being chiefly 

 giddiness and confusion in the head. 



In biology, as in all the more complicated branches of inquiry, 

 progress can only be made by a careful combination of the deductive 

 method with the inductive, and by bringing the powerful aid of the 

 imagination, kept, of course, in due and rigid subordination, to assist 

 the faculties of observation and reasoning ; and there are periods in 

 the history of every science when a false hypothesis is not only better 



