APPARATUS FOR PHYSIOLOGICAL USE. 267 



muscle, or of the muscles of the whole body ; but we must 

 remember that the muscles, like a steam-engine, not only 

 require oxygen, but fuel, and how are they to obtain this 1 

 The fuel is food, and in an ordinary meal consists, let us say, 

 of a beefsteak, bread, butter, and sugar. Now, how are these 

 to be dissolved, and how are they to be made available for the 

 muscles ? If you consider that they are in a solid condition, 

 and that they have to pass through animal membranes, from 

 the stomach and intestines into the blood that they have 

 to be in a state not merely of fine division, but in a state 

 of very perfect solution, you will see it is not such an easy 

 matter to provide the fuel for the muscles. Moreover, they 

 require to be not only dissolved so as to allow them to pass 

 into the blood, but broken up into other bodies having 

 generally a simpler chemical composition so as to allow the 

 muscles to assimilate them. A chemist could break them 

 up by using strong heat or powerful acids, but neither of 

 these means could be used by an animal body without 

 undergoing destruction itself, and so the food is decomposed 

 in another way which seems to me to bear the same relation 

 to the violent methods of the chemist, that a plan of 

 quarrying employed by the ancient Egyptians bears to the 

 rude blows of a gang of powerful navvies. When those 

 strange old people wished to cut an obelisk from a granite 

 quarry, they simply cut a small groove in the direction in 

 which they wished to split the obelisk. They drilled small 

 holes in these grooves, and into the holes they put wooden 

 wedges. Then they poured water into the grooves; the 

 wooden wedges swelled up, and by their expansion burst 

 the obelisk from the mass of living rock to which it was 

 joined. Now foods are broken up in the animal body by 

 substances termed ferments, which I think may be fairly 

 compared to the wedges of the ancient Eygptians, as they 

 do their work most efficiently, and with an expenditure of 

 apparently very little force. For example, I have here 

 some fibrine obtained by whipping blood. A chemist could 

 decompose this by putting it into dilute hydrochloric acid, 

 and then applying strong heat under pressure ; but I can 

 effect the same decomposition much more quickly without 

 raising the temperature above that of the body if I simply 

 add to the hydrochloric acid a little pepsin, the ferment con- 

 tained in the stomach. The decomposition which occurs 



