Chap, v.] CONSTITTTTION OF ORGANISED BODIES. 39 



having each special activity and special functions. These ana- 

 tomical elements are conformed in accordance with a small number 

 of types, and in the superior organised beings they are grouped 

 in tribes, and thus form tissues, charged each to fulfil such and 

 such great physiological function, which is the total of all the 

 elementary activities (muscular tissue, nervous tissue, osseous 

 tissue, chlorophyllian tissue of plants). 



As a matter of course the degree of differentiation in plants is 

 very variable. It is an organic law that this differentiation of 

 the anatomical elements is earned the further the more the 

 organised individual is perfect. In other words, the great law 

 of the division of labour reigns everywhere in the organised 

 world. Besides, the elements themselves have a more complicated 

 structure the more their function is complex (muscular fibre, 

 nervous fibre). Finally, the more the organisation of an animal, 

 taken as a whole, is simple, the simpler is also the structure of 

 each of the orders of anatomical elements. Thus the muscular 

 fibres of the radiata, the armulata, the mollusca, the nervous 

 tubes, the ganglionic cells of lampreys, are simpler than the 

 same elements in the crab.^ 



But in every superior organism there is a differentiated blend- 

 ing of anatomical elements, having varied functions and varied 

 degrees of structure. We could therefore, in every individual, 

 group the elements m series, according to their degree of perfec- 

 tion, of complication, and we should have a complete scale going 

 from the elements, confused and even amorphous, of the inferior 

 beings up to the elements with complex structure of the superior 

 beings.^ 



At the foot of the organic scale we find monocellular infusoria 

 (polytoma, difflugia, enchelys, monas, amoeba) formed of a single 

 homogeneous substance. Some of them are constituted of a sub- 



1 Ch. Eobin, BUments Anatomigues. 



'' Ch. Bemari, Eappart sur lesprogriset lamarcJiede la physiologie gin6rale 

 en Frama. Paris, 1867. 



