The Living Machine 



279 



One of the most characteristic features of life is its power 

 of waste and repair and growth. It is folly to attempt, as 

 some have done, to compare these processes in their entirety 

 with any process in the non-living world. There is nothing 

 with which they can be compared. And yet if we analyze 

 them into their component processes, we find that they are 

 composed of a series of chemical and physical reactions, many 

 of which at least can be exactly reproduced in the laboratory. 



In the warm spring days when the remnants of last year's 

 crop of potatoes in the cellar start to sprout, and those which 

 are served upon your table have an unpleasant sweetish taste, 

 you are the victim of a ferment known as diastase, of wide- 



Diagram illustrating osmosis through an egg membrane. Original. 



spread if not universal distribution among plants, which 

 changes starch, the stored-up food stuff of the plant, into 

 one of the sugars. When the maple sugar sap is flowing in 

 the spring we know that a similar action has been taking 

 place within the tree, and all the beauty of the young spring's 

 growth depends upon it. A similar action takes place in our 

 own stomach, under the influence of an animal ferment known 

 as ptyalin, and present in the saliva of many mammals. But 

 a similar result can also be obtained in the test tube of the 

 chemist by boiling starch in dilute acid. 



In order that the water of the soil with its dissolved salts 

 may enter the root, or the digested food stuffs in the intestine 

 pass into the streams of blood and lymph, the process of os- 



