34 THE BODY AT WORK 



together in the body, whether of a plant or of an animal 

 we are still unable to find any word other than body for 

 the thing as a whole tend more and more to differ in 

 appearance. Some are large, others small. Some have cell- 

 walls ; others have none. Some remain " protoplasmic " ; 

 others are largely composed of " metaplasm." Better terms 

 are wanted to connote " most living substance " and " less 

 living substance " respectively. It would be easy to coin 

 suitable words, but, alas ! the nomenclature of physiology is 

 already hopelessly encumbered, and there is little prospect 

 that a bad word will die when a good one is available in 

 its stead. Differences in structure indicate differences in 

 function. A division of labour has set in. The cell starts 

 with capacities for every function. Its particular situation 

 renders it desirable that ifc should cultivate one capacity at the 

 expense of the rest. It specializes in a particular direction. 

 If it happens to be placed in the centre of the body on the course 

 of the bloodvessels which bring to the embryo food and 

 oxygen from its mother, it develops a great capacity for taking 

 up food. It accumulates in its substance a vast quantity of 

 nutriment which it cannot consume, holds it, and passes it on 

 into the blood-stream as it is required. Thus the liver is 

 formed. In the embryo it attains to a great size, equal to 

 about one-half the whole body-weight ; but whether storing 

 food be its chief function at this stage, or whether the other 

 special functions for which it is responsible are equally im- 

 portant, remains a question for further research. In subse- 

 quent life its main work is to store food. After birth, when the 

 child prepares its own food by processes of digestion in its 

 stomach and intestines, the blood -supply of the liver is so 

 modified that the blood from the digestive organs is passed 

 through it. Now and for the rest of life the liver is the store- 

 house of food, the larder of the body. It is a reservoir from 

 which supplies are distributed as required. A liver-cell retains 

 many primitive characters. It is soft and destitute of envelope. 

 But under the microscope it appears, unless it be taken from 

 a starving animal, unlike any other cell (Fig. 7). It is always 

 loaded with masses of glycogen. Sometimes it contains fat 

 globules also. This is perhaps the simplest of all instances 

 of specialization of function. An amoeba can take up food. 



