48 BIOLOGY. [BOOK i. 



anatomical animal elements have forms much more varied. In 

 those of them which merit the name of fibre*, there is often no 

 longer any trace of the cellular form ; and the animal fibres are 

 not even derived from original cellular elements, if we admit 

 with M. Ch. Robin the spontaneous genesis of the anatomical 

 elements in the blastemas. 



This theory of the spontaneous apparition of the anatomical 

 elements in the living liquids has hitherto been rejected in 

 Germany, where is adopted in all its rigour the axiom of M. 

 Virchow Omnis celhda e cellula. 



In accordance with the terms of the German cellular theory, 

 every anatomical element, whatever it may be, has as origin 

 a cell ; it comes forth from it by gemmation or segmentation ; 

 and every element which departs from the cellular form is simply 

 a metamorphosed cell. It is not easy to understand how asser- 

 tions so directly opposed should be passionately maintained on 

 both sides by observers equally skilful. We are compelled to 

 admit that on each side there is a portion of truth. We 

 shall see when treating of generation that the French school 

 wishes to reject reproduction by division and gemmation in the 

 vegetal kingdom, in the initial period of embryonic animal life, 

 and in certain produced elements. According to this school, most 

 of the elements called constituent, that is to say, forming really 

 the framework of the animal organism, spontaneously arise, by 

 synthesis, by genesis in the living liquids, alike in the embryon 

 and the adult. 



Let this be as it may, the cellular theory is convenient for 

 classifying the anatomical elements. In effect, while the parti- 

 sans of spontaneous genesis admit no bond of direct kinship 

 among most of the anatomical elements, strive especially to note 

 dissemblances and to multiply species, the partisans of the cellular 

 theory, preoccupied with the idea of a common origin, dwell 

 especially on resemblances, and thus arrive at forming a very 

 small number of elementary histological groups. According to 

 them there are only four types of anatomical elements and of 



