OF VITAL PHENOMENA 7 



The burning of 1 g monosaccharide yields 3.74 large calories, 

 disaocharide 3.95, animal or vegetable fat 9.5, animal protein 

 5.7. All of this heat is produced by their burning in the body, 

 except in case of protein, which produces only 4.5 calories as it is 

 not completely burned, being eliminated as urea and uric acid 

 and ammonia, etc. 



The mineral constituents are apparently for the most part dis- 

 solved in the water contained in the cell and will be considered 

 later in regard to their effect on the solubilities (aggregation 

 states) of the proteins and phospholipines. 



Among those constituents occurring only in traces the most 

 important are the enzymes, thermolabile substances of unknown 

 composition which accelerate certain chemical reactions. Some 

 of the enzymes are poured out of the cells (as pepsin, for in- 

 stance) so that they may be easily obtained, but many enzymes 

 that are supposed to exist in all cells have been looked for in 

 vain. Such are the enzymes that are supposed to accelerate the 

 oxidation of the foodstuffs. It now appears that such oxidations 

 are inseparably connected with the cell structure or to some sub- 

 stance that is destroyed when the cell structure is destroyed. The 

 enzymes are greatly influenced in their activity by the hydrogen 

 ion concentration. They may be rendered inactive by adsorption, 

 or by anesthetics and they are influenced to some extent by neu- 

 tral salts. 



Most of the constituents of cells are called colloids on account 

 of their physical properties. Colloids are divided into two 

 classes, suspensoids and emulsoids. Suspensoids are merely 

 solid particles electrically charged and 'suspended in water, only 

 distinguished from suspensions by the small size of the particles, 

 which cannot usually be seen with the ordinary microscope but 

 only with the ultramicroscope with a powerful dark ground 

 illumination. The suspensoids are precipitated by small quantities 

 of neutral salts or other electrolytes (substances which dissociate 

 into ions), because ions of opposite charge to the particles collide 

 with them and neutralize their charge, the particles gravitating, 

 no longer having the electric charges to hold them up. 



Emulsoids are very different in some ways. The colloidal par- 

 ticles partly dissolve. The remainder absorbs water and swells, 

 becoming viscid and the result is an ultramicroscopic emulsion 



