LECTURE 1 1 1. 
STARCH. 
Starch, which performs a similar office in the economy 
of plants to that of fat in animals, is a most important 
ingredient in the aliment of the whole human race, two- 
thirds of mankind subsisting almost exclusively upon it ; 
its existence was known to the ancients. Leeuwenhoek 
first examined it microscopically in wheat and beans, 
and has given tolerably accurate representations of the 
granules in the second volume of his works. Starch is 
found in the cells of plants in the form of granules, as 
in Fig. 19, g, from the Rhubarb, the cells of which have 
been separated by maceration ; also in a section of a 
Potato. It is usually obtained by rupturing the cell- 
walls and washing out their contents with cold water ; 
when dry it is hard, and if rubbed between the fingers, a 
peculiar crackling sound is produced. Starch is inso- 
luble in cold water, alcohol, ether, volatile and fixed oils ; 
boiling water, however, changes its properties, causing 
