7 
which are readily passed (absorbed) through the Rion of the 
alimentary tract into the blood, or lymph, or both, and which 
ji in the cell structures. From the circulation these simple 
“construction units” are taken up and utilized by the cells in 
all parts of the body in the constructive operations that character- 
ize the extensions of development, the substitutions of mainte- 
nance, the depositions of accumulation, and the repairs of self- 
preservation. 
I. Alimentary digestion is a process of progressive conversion 
of complex compounds into comparatively simple substances 
The digestive juices are the mechanical media, and the enzymes 
in the juices are the chemical agents, in these peer ce 
digestive Lees es, which are collectively called ‘‘hydro- 
lases,”’ induce rapid reaction between the carbohydrates, lipins 
and proteins on one side and water on the other: hydrolysis 
ensues. The enzymes themselves are not consumed in the proc- 
ess; they are agents that order things about into new relationships. 
Through the influence of hydrolases, by their direction let us 
say, water molecules are driven into, so to speak, and break with, 
the molecules of the digestible substances, hydroxyl from the 
water passing into one part of a cloven complex molecule, hydro- 
gen entering the other. This process continues nae the large 
molecular blocks are chopped into very small fragmen hus 
the molecule of cane sugar (CwH2On), which may be eee 
by the formula CeHuOse—CeHuOs, is converted into glucose 
and fructose, by the enzyme sucrase in intestinal juice, in 
harmony with the cleavage indicated by the following general 
equation: 
CeHnOe—CeHnO; + aa CeH 206 + ee 
Can ar Wat Glucuse 
(CeHuOs +H) (cee on) 
e hydrogen and hydroxyl of the water are divided, in this 
reaction, between the two isomeric hydrolytic products, glucose 
and fructose. 
In similar reactions, starches, cane sugar, fats and albuminous 
substances (the leading representatives of the types of substances 
