Immediately after slaughter, meat has an alkaline reaction and is found to be tough and of a sweetish taste and of a somewhat unpleasant flavor. Sarcolactic soon develops, giving an acid reaction to the meat. Autolytic enzymes soon form and this action, together with the bacterial action, softens the connective tissue and fibers. This results in the meat becoming more tender and also of a more desirable flavor. For these reasons meat should be allowed to remain under proper refrigeration for a sufficient length of time so that this action can take place. It is obvious, therefore, that meat is not so desirable for food immediately upon slaughter. Great care must be taken during the period of refrigeration that it does not become contaminated. Food Value of Meat The presence of proteins and fats in meat determines its nutrient value. Nitrogenous extracts, also known as meat bases, have but little value as foods. As already stated, meat compares more favorably with seeds that are used for diet rather than the leaves of plants. As a matter of fact, this food, more particularly muscle tissue, differs from seeds only in one respect. This is in the quality of proteins. In meat the proteins are complete while those of seeds are incomplete. Meat is relatively poor in the vitamin, fat soluble A. There are many articles of diet which have a much higher nutritive value than meat. There is prepared from beef a soup stock which is known as beef extract. Manufacturers of this soup stock assert that one pound of beef extract contains the nutrient properties of many pounds of meat. Doctor Wiley, however, says that this assertion is erroneous. These extracts are of value since from them there may be obtained a more speedy, soluble nutrient which may be desirable for patients in a weakened condition. There should be a distinction, however, made between beef extract and beef juice. Beef juice is obtained by putting the meat under pressure and forcing the juices out. Thus, this juice contains a larger percentage of albuminous nutrient material than does beef extract. Sources of Meat Cattle, sheep and swine form the principal source of meat, although horse flesh and even the flesh of dogs is used in some countries. From a hygienic or sanitary standpoint there are no particular objections to the use of horse or dog meat for food. Horse meat is very much coarser than either beef or pork; it does not have the same marble appearance and has a sickening odor. When properly prepared it is difficult to distinguish it from beef. From a hygienic standpoint there are certain conditions which render the meat of animals unfit for food. They are: First, the death of animals from old age, dis-ease or accident; second, animals dying from injury, drugs, overwork or fright; third, animals that are too young. Care of Food Animals Proper care of the animal bears a close relationship to its health and consequently to the health of the people who feed upon its flesh.