22 PRESIDENTS ADDRESS. 



composed of certain chemical compounds, as proteins, carbo- 

 hydrates, or fats, we are aware that this material has been part 

 of the animal or vegetable body. Life is thus associated with a 

 particular architecture built with characteristic chemical sub- 

 stances. AVhile the qualities and properties of living things ap- 

 pear so different from those of lifeless matter, the biochemist soon 

 discovers that all living things are constructed from lifeless sub- 

 stance. As an animal or plant grows, it adds to its bulk material 

 from the inanimate world. All the carbonaceous material in the 

 protoplasm of the cells of all living objects contains carbon once 

 diffused through the atmosphere as carbon dioxide. For a brief 

 period this carbon is found in some animal or plant. Perhaps it 

 in the green leaf of a growing wheat-plant. A few weeks later, 

 it lies in the golden grain. The farmer harvests that grain and 

 sends it to the miller. The same carbon is part of a particular 

 sack of flour, delivered to a baker. It is portion of some loaf of 

 bread eaten by John Smith. It is the carbonaceous constituent 

 of «iluco8e in the blood of John Smith. It is combusted in some 

 part of John Smith's body, and it is dissolved as carbon dioxide 

 in his blood. It diffuses through the epithelium of his lungs. It 

 goes out again into the atmosphere in the expired breath of the 

 individual. Some day it will be taken up by another plant, and 

 so on in an endless cycle. It is difficult to suppose that this 

 carbon becomes endowed with new qualities while it lies in the 

 living tissues <jf the animal or plant. It is necessary to seek some 

 other explanation of the characteristic properties of living things. 

 It has long been obvious that animals and plants make the 

 chemical constituents of their bodies from raw materials by dif- 

 ferent processes from those used in the chemical laboratory or in 

 the factory for the manufacture of similar substances. Heat and 

 pressure, so freely used in the synthesis of bodies akin to those 

 found in living things, play no part in the manufacture of starch, 

 fat, or protein in a plant. We have a dim idea that those in- 

 tangible materials, known as ferments, are chiefly concerned with 

 vital synthesis. In fact, the presence of ferments and the capacity 

 to produce ferments appears to be one of the most distinctive 

 chemical characters of living matter. Ferments bring about 



