THE VITAL PROPERTIES OF THE CELL 129 



(anaerobic Bacteria, etc.) the respiration of oxygen is a funda- 

 mental characteristic of the whole of organic nature, being abso- 

 lutely necessary for the continuance of the metabolic processes 

 upon which life depends, and through which by the oxidising of 

 complex molecular compounds the vital forces must be produced. 

 As a rule the lack of oxygen very quickly arrests the functions 

 of the cell (its irritability, powers of movement, etc.) : and finally 

 death of necessity ensues. 



Some of the fermentation organisms, the fission and pullulating fungi, appear 

 to form an exception to this fundamental process of respiration. For they are 

 able to grow and multiply in a suitable nutrient fluid when completely shut off 

 from oxygen. In this case, however, the oxygen necessary for the oxidation 

 processes in the protoplasm is obtained through tbe decomposition of the fer- 

 menting substance. Similarly intestinal parasites are able to exist in an 

 environment comparatively free from oxygen by splitting up of compounds of 

 which a superfluity is supplied to them (Bunge V. 2). 



What is the part played by the oxygen after it has been taken 

 up by the cell? 



It was formerly believed that the oxygen directly oxidised the 

 living material, so that, as it was figuratively expressed, a pro- 

 cess of combustion was called forth, as the result of which heat 

 was given off. However, there seems to be little doubt but that 

 the forces which result in the combination of the oxygen origi- 

 nate in the vital substance itself. In this mixture of special 

 albuminous bodies, and their derivatives, which goes under the 

 name of protoplasm, and in which, moreover, fats and carbo- 

 hydrates are stored up, important molecular re-arrangements and 

 re-groupings of atoms, often the result of very minute exciting 

 causes, take place ; amongst these, decomposition and dissocia- 

 tion occur. " Under these circumstances many decomposition 

 products continually develop an affinity for free oxygen (oxidative 

 decomposition), and it is in this way that oxygen takes part in the 

 process of metabolism " (Pfiuger V. 25, 26). Hence in conse- 

 quence of respiration, and at the cost of the organic substance, 

 combinations rich in oxygen are produced ; and finally, through 

 the repeated dissociation and oxidation of these substances, carbon 

 dioxide and water, the most important final products of the de- 

 structive processes of living substance during respiration are 

 produced. 



This is true for every animal and every plant cell. 



If plant cells (staminal hairs of Tradescantia, cells of Characese), 



K 



