THE CHEMICAL UNITY OF LIVING BEINGS. 175 



or the framework of the albuminoid molecule; in 

 other words, its chemical nucleus. 



Physical Characters of Protoplasm. — About i860 

 Ch. Robin thought that he had defined living matter 

 sufficiently — or, at least, as perfectly as could be 

 expected at that time — by attributing to it three 

 physical characteristics. They were : — Absence of 

 homogeneity, molecular symmetry, and the association 

 of three orders of immediate principles — albuminoids, 

 carbohydrates and fats. These characteristics assist, 

 but do not suffice, to define the organization. 



No doubt the characteristics must be completed by 

 the addition of a certain number of more subtle 

 physical features. 



One of them refers to the structure of protoplasm 

 as revealed by the microscope. Throughout the 

 whole of the living kingdom, from the bacteria studied 

 by Kunstler and Busquet to the most complicated 

 protozoa, protoplasmic matter presents the same 

 constitution, and in consequence, this structure of 

 the protoplasm must be considered as one of its 

 distinctive characters. It is not homogeneous ; it 

 is not the last term of the visible organization : it is 

 itself organized. Experiment shows that it does not 

 resist breaking up or crushing. Mutilations cause 

 it to lose its properties. As for the kind of structure 

 that it presents, it may be expressed by saying that it 

 is that of a foamy emulsion. 



We saw above that our knowledge as to the physical 

 condition of protoplasm has been completed by the 

 theories of Biitschli's micellae or Pfefifer's tagmata. 



Properties of the Protoplasm. Its Affinity for 

 Oxygen. — From the chemical point of view, living 

 matter presents a very remarkable property — namely, 



