breathe than from foreign substances in the food we eat.

But whence come the much less minute amounts of tin--still harmless, be
it remembered--which have been stated to be occasionally present in
canned foods? They come from the minute particles of metal chipped off
from the tin sheets in the operations of cutting, bending, or hammering
the parts of the can, or possibly melted off in the operations necessary
for the soldering together of the joints of the can. Some may, perhaps,
be cut, off by the knife in opening a can. At all events I not
unfrequently find such minute particles of metal on carefully washing
the external surfaces of a mass of meat just removed from a can, or on
otherwise properly treating canned food with the object of detecting
such particles. The published processes for the detection of tin in
canned food will not reveal more than the amounts stated in the table,
or about those amounts; that is to say, a few thousandths or perhaps two
or three hundredths of a grain, if this precaution be adopted. If such
care be not observed, the less minute amounts may be found. I did not
detect any metallic particles in the twelve samples of canned food just
mentioned, but during the past few years I have occasionally found small
pieces of metal, perhaps amounting in some of the cases to a few tenths
of a grain per pound. Now and then small shot-like pieces of tin, or
possibly solder, may be met with; but no one has ever found, to my
knowledge, such a quantity of actual metallic tin, tinned iron, or
solder as, from the point of view of health, can have any significance
whatever.

The largest amount of tin I ever detected in actual solution in food was
in some canned soup, containing a good deal of lemon juice. It amounted
to only three-hundredths of a grain in a half pint of the soup as sent
to table. Now, Christison says that quantities of 18 to 44 grains of the