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From these sources it is obtained as food. Glycogen, a substance closely resembling starch, is found in the body of the oyster. Glycogen is, on this account, called animal starch. Starch on being eaten is first changed to sugar, after which it may be converted into glycogen in the liver and in the muscles.
The cells obtain their materials from the lymph, and the lymph is supplied from the blood. Should food substances, such as sugar, increase in the blood beyond a low per cent, they are converted into a form, like glycogen, in which they are held in reserve, or, for the time being, placed beyond the reach of the cells.
Nowadays, glycogen and the blood sugar are not considered internal secretions, because they are classified as elementary reserve food, while the concept of the internal secretions has become narrowed down to substances acting as starters or inhibitors of different processes.
To provide against emergencies, and to keep up a uniform supply of food to the cells, it is necessary that the body store up nutrients in excess of its needs. *Methods of Storage.*—The general plan of storage varies with the different nutrients as follows: 1. The carbohydrates are stored in the form of glycogen.
The increased output of adrenalin activates the brain to still greater activity, as a result of which again the entire sympathetic nervous system is further activated, as is manifested by increased heart action, more rapid respiration, raised blood-pressure, increased output of glycogen, increased power of the muscles to metabolize glucose, etc.
He discovered the glycogenic function of the liver, and proved that in addition to secreting bile, that organ stores up glycogen from the sugar absorbed in the stomach and intestines, and gives it out again as sugar to the blood. In 1855 he maintained that every organ of the body by a process of internal secretion gives up products to the blood.
On account of the nature of the urea and the bile, the liver is properly classed as an excretory organ; but in the formation of the glycogen it plays the part of a storage organ. Then, on account of the use made of the bile after it is passed into the food canal, the liver is also classed as a digestive organ. These different functions make of the liver an organ of the first importance.
The amount of glycogen in the liver was diminished in all the experiments showing brain-adrenal activity; and when the histologic changes were repaired, the normal amount of glycogen was again found. In crossed circulation experiments changes were found in the liver of the animal whose brain received the stimulus.
You are aware that there is a substance, called waxy matter, which is deposited in the tissues of the body during the course of certain diseases. What this may be and how it is formed has been a cause for much bickering among pathologists. Cullingworth had strong views upon the subject, holding that the waxy matter was really the same thing as the glycogen which is normally secreted by the liver.
Moreover, the process of liberation of sugar from glycogen itself in the liver, upon demand, is today set down to the action of an internal secretion, adrenalin. Claude Bernard's conception, like a novelist's characters, has turned upon its creator, taken on a life of its own, and evolved into something he never intended.
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