40 LECTURE I. 



of quite a peculiar conformation, as a definite basis for 

 all the phenomena of life. 



According to my ideas, this is the only possible start- 

 ing-point for all biological doctrines. If a definite cor- 

 respondence in elementary form pervades the whole series 

 of all living things, and if in this series something else 

 which might be placed in the stead of the cell be in vain 

 sought for, then must every more highly developed 

 organism, whether vegetable or animal, necessarily, 

 above all, be regarded as a progressive total, made up of 

 larger or smaller number of similar or dissimilar cells. 

 Just as a tree constitutes a mass arranged in a definite 

 manner, in which, in every single part, in the leaves as 

 in the root, in the trunk as in the blossom, cells are dis- 

 covered to be the ultimate elements, so is it also with 

 the forms of animal life. Every animal presents itself as 

 a sum of vital unities, every one of which manifests all 

 the characteristics of life. The characteristics and unity 

 of life cannot be limited to any one particular spot in a 

 highly developed organism (for example, to the brain of 

 man), but are to be found only in the definite, constantly 

 recurring structure, which every individual element dis- 

 plays. Hence it follows that the structural composition 

 of a body of considerable size, a so-called individual, 

 always represents a kind of social arrangement of parts, 

 an arrangement of a social kind, in which a number of 

 individual existences are mutually dependent, but in 

 such a way, that every element has its own special 

 action, and, even though it derive its stimulus to activity 

 from other parts, yet alone effects the actual performance 

 of its duties. 



I have therefore considered it necessary, and I believe 

 you will derive benefit from the conception, to portion 

 out the body into cell-territories (Zellenterritorien). I 

 say territories, because we find in the organization of 



