A Practical Physiology

roportion to form water. Thus we have animal starch, or glycogen, stored up in the liver. Sugar, as grape sugar, is also found in the liver. The body of an average man contains about 10 per cent of Fats. These are formed of carbon, hydrogen, and oxygen, in which the latter two are not in the proportion to form water. The fat of the body consists of a mixture which is liquid at the ordinary temperature.

Now it must not for one moment be supposed that the various chemical elements, as the proteids, the salts, the fats, etc., exist in the body in a condition to be easily separated one from another. Thus a piece of muscle contains all the various organic compounds just mentioned, but they are combined, and in different cases the amount will vary. Again, fat may exist in the muscles even though it is not visible to the naked eye, and a microscope is required to show the minute fat cells.

10. Protoplasm. The ultimate elements of which the body is composed consist of "masses of living matter," microscopic in s