DEFENSIVE FERMENTS OF THE ANIMAL ORGANISM II 



cells, a forecast of the division of labour found 

 amongst the organs of the higher forms of life. In 

 the former case we have the cells as yet free, while in 

 the latter they are combined into tissues. From this 

 point of view we may look upon the symbiosis of 

 heterogeneous species of cells as a first experiment in 

 the building up of a cell state. The single cells are 

 still independent and their duties multifarious. 

 There is no strong bond uniting the organisms into 

 any one "organ,' and yet they depend upon each 

 other for mutual support. Unicellular beings begin 

 to organize themselves into combinations. Another 

 step further and we arrive at cell complexes having 

 definite functions, which we call organs. But even 

 the most developed organisms, both of the animal and 

 plant worlds, have relations with cells which stand 

 outside the common organization. By means of 

 micro-organisms the plant gains access to otherwise 

 inaccessible sources of nitrogen, while by means of 

 bacteria the animals make use of the important carbo- 

 hydrate, cellulose. The bacteria convert the latter, 

 within the intestines, into products which can be 

 further decomposed by the ferments secreted by the 

 glands. 



In those organisms in which division of labour has 

 been instituted amongst the cells, and particularly 

 in those in which definite cells have closed in to form 

 an alimentary canal, these are the only cells which 



