INTRODUCTION. 



§ i. 



The doctrine of the elementary structure of Plants and 

 Animals, belongs to the last two centuries, originating with 

 Marcellus Malpighi (1628-94), and Anton van Leeuwenhoek 

 (1632-1723), at the period when the assistance of magnifying 

 glasses, powerful, though of very simple form, was first offered 

 to observers. The ultimate constituents in respect of form, of 

 organisms, were unknown to antiquity and to the middle ages, 

 for although Aristotle and Galen speak of the homogeneous 

 and heterogeneous parts of the body (partes similares et dis- 

 similares), and Fallopius (1523-62) defined still more exactly 

 the idea of " Tissues," and even attempted to classify them, 

 ( f Tractatus quinque de partibus similaribus/ opera, torn, ii, 

 Francof. 1600), yet the minuter structures were completely 

 hidden from these investigators. Brilliant as were the first 

 efforts of young science under the guidance of these men and 

 afterwards of a Ruysch, Swammerdam and others, yet they 

 were not adequate to acquire a safe footing for it, since, on 

 the one hand, the philosophers were far too little masters of 

 microscopic investigation to strive at once, with clear insight, 

 towards the true goal ; while, on the other, the development 

 of other branches of study, as of the grosser Anatomy, of 

 Physiology, of Embryology and of Comparative Anatomy, 

 claimed too large a share of their attention. It thus happened 

 that, with the exception of a few to some extent important works 

 i. 1 



