When lean meat is heated its myosin is converted into a solid insoluble substance much like the white of a hard-boiled egg. Hence, when a muscle is boiled most of its proteid is coagulated and stays in the meat instead of passing out into the soup. Even if beef be soaked first in cold water this is still the case, as myosin is not soluble in water.* It follows that beef tea as ordinarily made contains little but the flavoring matters and salts of the beef, and some gelatin dissolved out from the connective tissue of the muscle. The flavoring matters make it deceptively taste as if it were a strong solution of the whole meat, whereas, it contains but a small proportion of the really nutritious parts, which are chiefly left behind in tasteless shrunken shreds, when the liquor is poured off. Some things dissolved out of the meat make beef tea a stimulant to the nervous system and the heart, but its nutritive value is small, and it cannot be relied upon to keep up a sick person's strength for any length of time.

What proportion of water does muscle contain? What other inorganic compounds do we find in it? What is the reaction of living muscle? How is this changed by work or death? What are its main organic constituents? Name the most abundant of these? What change occurs in it after death? What is syntonin?

What happens to the myosin when muscle is heated? When we boil meat does its myosin become dissolved in the soup? Can we get the myosin out of beef by soaking it in cold water? What things are found in ordinary beef tea?

* To get over this difficulty, various methods of making beef tea have been suggested, in which the chopped meat is soaked an hour or two in strong brine or in very dilute muriatic acid. In these ways the myosin can be dissolved out of the beef; but the product has such an unpleasant taste that no one is likely to swallow it. and least of all a sick person.

Liebig's extract of meat is essentially but a concentrated beef tea; from its stimulating effect it is often useful to persons in feeble health, but other food should be given with it. It contains all the flavoring matters of the meat, and its proper use is for making gravies and flavoring soups; the erroneousness of the common belief that it is a highly nutritious food cannot be too strongly insisted upon, as sick persons may be starved on it if ignorantly used.

Various meat extracts are now prepared by subjecting beef to chemical processes in which it undergoes changes like those experienced in digestion. The myosin is thus made soluble in water and uncoagulable by heat, and a real concentrated meat extract is obtained. Before relying on any one of them for the feeding of an invalid, it would, however, be well to insist on having a statement of its method of preparation, and then to consult a physician, or some one else who has the requisite knowledge, in order to ascertain if the method is such as might be expected to really attain the end desired.

Why does beef tea taste as if all the " strength " of the meat were in it? Where do the chief nutritious parts remain when beef tea is strained off the meat ? What is the action of beef tea on the system ?

What is Liebig's extract of meat ? Why is it sometimes useful to invalids? What should be given them in addition? What is its proper use? Why is it important to know that it is not a nutritious food?

How are some other meat extracts made? How is the myosin changed in preparing them ? Are they all to be relied on indiscriminately? What should be done before trusting the nutrition of a feeble person to any one of them ?