322 HOW TO WORK 



and, in fact, by passing through the condition, of a, figs. 370, 371, 

 pi. LVIII. So far, then, it would seem that in the process of nutrition 

 pabulum passes into living germinal matter, and is converted into this 

 substance. The formed material or tissue which, in many cases, 

 constitutes the chief increase in weight and bulk, has all passed 

 through the state of germinal matter. The formation of this ger- 

 minal matter from the pabulum is therefore the important part of 

 the nutritive process. Similar changes occur in the nutrition of the 

 simplest living creatures as well as in the most complex. In the 

 higher animals the food introduced into the stomach becomes dis- 

 solved, and the solution is taken up by the germinal matter of the 

 villi, the chyle corpuscles, and the white blood corpuscles. Changes 

 occur in these masses of germinal matter, and the products resulting 

 form the pabulum for the germinal matter which takes part in the 

 formation of the various textures. 



Of the Action of the Cell. Now there can be no doubt that the 

 action of many cells is due to the chemical changes exerted by oxygen 

 upon the formed material. This gas combines with some of the 

 elements and new compounds which often constitute the "secretion " 

 of the cell are formed. It will be observed that the material to be 

 oxydised is first formed through the agency of the germinal matter as 

 has been already explained. The view has been generally accepted 

 that oxygen is necessary to life. It is, however, certain that the 

 principal demand for oxygen in living beings arises from the necessity 

 for chemical change and destruction of material which is formed in 

 consequence of the vital changes occurring in the germinal matter. 

 Oxygen acts principally upon the surface of cells, upon the oldest 

 part of the formed material, rather than upon the germinal matter 

 embedded in it. It seems that the formed material is prevented 

 from accumulating round the germinal matter of many cells by exter- 

 nal agencies, among which the oxydising action of oxygen 'is the 

 most important. In this way the formed material becomes resolved 

 into more soluble substances, which are at once removed. Thus 

 the passage of pabulum through the formed material and its access 

 to the germinal matter are facilitated. 



A cell may undergo the most active change without altering in 

 size. The absorption of pabulum and the production of new germinal 

 matter may be compensated for by the conversion of the latter into 

 formed material, as the old formed material becomes oxydised and 

 removed from the cell. Oxygen acts upon the lifeless matter tf the cell 

 rather than upon that which lives. It does not support life directly, but 

 is necessary to the continuance of life, because it alone can convert 

 the products of death and decay into soluble substances, which can 



