PRESIDENTIAL ADDKESS. 



21 



toplasm we know. In 1913, Sir Oliver Lodge, who suc- 

 ceeded Sir Edward Schaefer as President of the British 

 Association, took the view that (11) " Life introduces an 

 incalculable element." 



There is a power of adjustment to external circumstances 

 in living things, a co-ordination of all the parts and their 

 properties for the good of the whole, which may well make 

 some of us despair about the creation of living from non- 

 living matter. 



In the living organism, plant or animal, the building up 

 and breaking down of tissues are essentially chemical pro- 

 cesses; if any difference is to be drawn between these and 

 ordinary chemical processes outside the organism ("in 

 vitro,") it is that the reactions in living things are carried 

 out with such surprising ease on account of the catalytic 

 enzymes present, and that we are unable as yet to produce 

 the enzymes by any synthetic process in vitro. 



Elements required by plants and animals. 

 The elements used by animals and plants in building up 

 their tissues are comparatively few, and of low atomic 

 number. They are Hydrogen (No. 1), Oarbon (No. 6), 

 Nitrogen (No. 7), Oxygen (No. 8), Sodium (No. 11), Mag- 

 nesium (No. 12), Silicon (No. 14), Phosphorus (No. 15), 

 Sulphur (No. 16), Chlorine (No. 17), Potassium (No. 19), 

 Calcium (No. 20), Manganese (No. 25), Iron .(No. 26). 



Small quantities of other elements are found in special 

 cases, but with the exception of iodine, elements of large 

 atomic number are not usually found in living things, these 

 elements and their compounds being more or less toxic to 

 protoplasm. Some of the elements just quoted are indis- 

 pensable for the growth of living things. These indispens- 

 able elements are however not the same in all cases. 



Yeast, a very humble form of life, requires only hydrogen, 

 <jarbon, nitrogen, oxygen, magnesium, potassium, and 

 phosphorus. 



