202 THE ATMOSPHERE 



into varying intermediary products, the sources of muscular, 

 nervous, and secretory, activity, conversions which signify mani- 

 fold chemical processes. The living cell, wonderful in its minute- 

 ness, is capable of the most extraordinary number of chemical 

 reactions, many of which run in opposite directions. The liver 

 cell, for example, builds glycogen out of sugar, and sugar out 

 of glycogen, forms urea and uric acid out of amido-acids and 

 ammonia, breaks down haemoglobin, separating iron and form- 

 ing bilirubin, produces cholalic acid out .of unknown precursors 

 and links it with taurin and glycin, and binds phenol with the 

 radicle of sulphuric acid. These are the chief known activities ; 

 in addition there are hosts of others, including the assimilation, 

 hydration, and oxidation of food-stuffs. In the laboratory such 

 chemical reactions can only be carried out with the different 

 reagents separated in many vessels, with the aid of heat and 

 other physical agencies, acids, alkalies, &c., used as activators, 

 and many laboratory appliances. In the cell we are confronted 

 with an astounding simplicity of structure, and a mechanism 

 which spares space and energy to a marvellous degree. 



Hofmeister suggests that the fundamental principle of this 

 structure is the existence of innumerable enzymes, or precursors 

 of enzymes, of a colloidal nature, which are fixed in the 

 colloidal bioplasm owing to their non-diffusible nature. The 

 cell is formed like a foam-structure, and the colloidal enzymes, 

 being separated by the impermeable membranes of the foam, 

 give a chemical organisation to the cell and allow an orderly 

 progression of chemical reaction. If we conceive that the 

 products of one reaction activate another enzyme, which starts 

 a second reaction, and so on in progression, the sequence of 

 activity is explained in a plausible way. The cells, owing to 

 their colloidal structure, are continually permeated by a current 

 of diffusible substances, which sets from blood to lymph, a 

 watery solution of oxygen, salts, sugar, glycogen, &c. The 

 reactions take place between the enzymes and the contents of 

 this current. Nothing but a colloidal structure would allow 

 such a complication of organisation to be confined in the 

 smallest space, together with permeability to non - colloids. 

 The kinetic energy of living organisms is obtained from the 

 enzymic decomposition either of the bioplasm itself or of the 

 non-colloidal food-stuffs that permeate the bioplasm. The quick 



