IS THE BODY A MACHINE? 45 



while we do not yet know very much about 

 them, they are of the same sort as those of 

 digestion, and involve probably nothing more 

 than chemical processes. 



Secondly, we notice that there is one phase 

 of absorption which is still obscure. Part of 

 the food is composed of fat, and this fat, as 

 the result of digestion, is mechanically broken 

 up into extremely minute droplets. Although 

 these droplets are of microscopic size they are 

 not actually in solution, and therefore not sub- 

 ject to the force of osmosis which only affects 

 solutions. The osmotic force will not force fat 

 drops through membranes, and to explain their 

 passage through the walls of the intestine re- 

 quires something additional. We are as yet, 

 however, able to give only a partial explanation 

 of this matter. The inner wall of the intestine 

 is not an inert, lifeless membrane, but is made of 

 active bits of living matter. These bits of living 

 matter appear to seize hold of the droplets of oil 

 by means of little processes which they thrust 

 out, and then pass them through their own 

 bodies to excrete them on their inner surface 

 into the blood-vessels. Fig. 5 shows a few of 

 these living bits of the membrane, each con- 

 taining several such fat droplets. This fat 

 absorption thus appears to be a vital process, 

 and not one simply controlled by physical forces 

 like osmosis. Here our explanation runs against 

 what we call vital power of the ultimate elements 

 of the body. The consideration of this vital 

 feature we must, of course, investigate further ; 

 but this will be done later. At present our 



