Supplement to the Tropical Agncuiturist." [JuLV 1, 190^. 
meat, bones, and gristle by the water. In ordin- 
ary meat broth these consist almost wholly of 
extractives and salts, which are very agreeable 
and often most useful as stimulants but have 
little or no value as actual nutriment, since they 
neither build tissue nor yield energy. The princi- 
ples which underlie the cooking of flsli are essen- 
tially the same as with meats. 
In many vegetables the valuable carbohydrates, 
chiefly microscopic storch grains, are contained in 
tiny cells with thick walls on which the digestive 
juices have little effect. The heat of cooking, 
especially with the aid of water, ruptures these 
walls and also makes the starch more soluble. 
The heat also catamelizes a portion of the carbohy- 
drates and produces agreeable flavors in this and 
other ways. 
In breads, cfikes, pastry, and other foods 
prepared from flour, the aim is to make a palatable 
and lighter porous substance more easily broken 
up in the alimentary canal than the raw materials 
could be. Sometimes this is accomplished simply 
by means of water and heat. The heat changes 
part of the water in the dough into steam, which, 
in trying to escape, forces the particles of dough 
apart. The protein (gluten) of the flour stiffens 
about the tiny bubbles thus formed and the mass 
remains porous even after the steam has escaped. 
More often, however, other things are used to 
"raise" the dough — such as yeast and baking 
powder. The baking powder gives off the gas 
carbon dioxide and the yeast causes fermentation 
in the dough by which carbon dioxide is produced. 
This acts as the steam does, only much more 
powerfully. When beaten eggs are used, the 
albumen incloses air in bubbles which expand, 
and the walls stiffen with the heat and thus 
render the food porous. 
Scrupulous neatness should always be observed 
in keeping, handling, and serving food. If ever 
cleanliness is desirable, it must be in the things 
we eat, and every care should be taken to insure 
it for the sake of health as well as of decency. 
Cleanliness in this connection means not only 
absence of visible dirt, but freedom from undesir- 
able bacteria and other minute organisms, and 
from worms and other parasites. If food, raw or 
cooked, is kept in dirty places, peddled from dirty 
carts, prepared in dirty rooms and in dirty dishes, 
or exposed to foul air, disease germs and other 
offensive and dangerous substances can easily 
get in. 
Food and drink may, in fact, be very dangerous 
purveyors of disease. The bacteria of typhoid 
fever sometimes find their way into drinking 
water, and those of typhoid and scarlet fevers and 
diphtheria into milk, and bring sickness and death 
to large numbers of people. Oysters which are 
taken from the salt water where they grow and 
"floated" for a short time in brackish water near 
the mouth of a stream, have been known to be in- 
fected by typhoid fever germs brought into the 
stream by the sewage from houses where the 
dejections from patients had been thrown into the 
drains. Celery or lettuce grown in soil containing 
typhoid germs has been thought to convey this 
disease. 
Food materials may also contain parasites, like 
tapeworms in beef, pork, and mutton, and trichinae 
in pork, which are often injurious and sometimes 
deadly in their effect. This danger is not confined 
to animal foods. Vegetables and fruits may 
become contaminated with eggs of numerous 
parasites from the fertilizers applied to them. 
Eaw fruits and vegetables should always be very 
thoroughly washed before serving if there is any 
doubt as to their cleanliness. If the food is 
suiBcieutly heated in cooking all organisms are 
killed. 
Sometimes food undergoes decomposition in 
which injurious chemical compounds, so-called 
ptomaines, are formed. Poisoning by cheese, ice 
cream, preserved flsh, canned meats and the like 
has been caused in this way. The ptomaines 
often withstand the heat of cooking. 
In some cases it has been found that foods are 
adulterated with compounds injurious to health; 
but sophistication in which harmless articles of 
inferior cost or quality are added is more common. 
Dainty ways of serving food have a usefulness 
beyond their aesthetic value. Everyone knows 
that a feeble appetite is often tempted by a taste- 
fully garnished dish, when the same material 
carelessly served would seem quite unpalatable. 
Furthermore, many cheap articles and " left-overs" 
when well seasoned and attractively served may 
be just as appetizing as dearer ones, and will 
usually be found quite as nutritious. 
Diets. — The information gained from a study of 
the composition and nutritive value of foods may be 
turned to practical account by using it in planning 
diets for different individuals or classes of indivi- 
duals, or in estimating the true nutritive ralue of 
the food actually consumed by families or indivi- 
duals. By comparing the results of many such 
investigations with the results of accurate physio- 
logical experimenting it is possible to learn about 
how much of each of the nutrients of common 
foods is needed by persons of different occupations 
and habits of life, and from this to compute 
standards representing the average requirements 
for food of such persons. 
During the last twenty years much of this prac- 
tical application of the chemistry of food has been 
made in the study of actual dietaries. Much 
work of this kind has been done in England, 
Germany, Italy, Russia, Sweden, and elsewhere 
in Europe, and iu Japan and other oriental 
countries- Within the past dozen years extensive 
studies have been made in the United States. 
The simplest way of making such inquiries is to 
find out what kinds and quantities of food are 
used during a given period in the household in 
which the study is made ; to estimate the amounts 
of various nutrients which the different materials 
contain by means of figures given for the average 
composition of the various articles in tables, like 
Table I (p. 16) ; and then to calculate the cost and 
amount of nutrients for each person. There are, 
however, several, chances for error in such a 
method. In the first place, since different speci 
mens of the same kind of food vary greatly in 
composition, it is often inaccurate to estimate the 
