This section is from the book "The Hygienic System: Fasting And Sun Bathing", by Herbert M. Shelton. Also available from Amazon: The Hygienic System Vol III Fasting and Sun Bathing.
The body's reserve stores are designed for use in just such emergencies and may be utilized in such circumstances with greater ease and with less tax upon the body than food secured through the laborious process of digestion. As Jennings explained:
"There is one particular in relation to the lymphatic system of vessels, that deserves special notice and remembrance. In some forms of impaired health, when the nutritive apparatus is disabled, either from defects in its own structure, that require suspension of its action for recuperative purposes, or because the only organic forces that can be used to sustain its action, are, for the time, either exhausted or employed more advantageously in other duties, the lymphatic vessels interpose their kind offices to supply the deficiency by taking up the adipose and fleshy substances wherever they can find them, or any matters that they can work up into nourishment, and throwing it into the general circulation to be distributed among the weary and hungry laborers according to their several necessities,--for they that work must eat. Indeed, this expedient is often resorted to in severe cases of illness, particularly in those of protracted general debility; for it is less expensive to the vital economy to furnish the requisite sustenance in this way, than to do it by the nutritive machinery from raw material. This wise provision for sustaining life under critical circumstances, should allay all fears and anxieties on the score of eating when there is a lack of appetite; for when there is a demand for nourishment, and the nutritive machinery is in working order, and the necessary forces can be consistently spared to operate it, there always will be appetite, and just in proportion to the necessities of the system for nourishment; for real genuine appetite is simply and only nature's appeal for something with which to supply a want, and if she makes no call, it is either because there is no want to be supplied, or she is not in a condition to meet it, and in either case it would be useless to urge food upon the stomach, either in repugnance to obvious indication, or after having provoked an unnatural appetite.
"In an extreme case, when it is expedient to make dependence on the lymphatic system for nutrimental aid for a long period, until all the material suitable for supply through that medium is exhausted, and starvation becomes the alternative to digestion and assimilation, if it is a remediable case, the nutritive system will be clothed with power sufficient to make a call for food, and on its reception, commence operations; it may be in a very slight degree for a while, and at intervals of some hours, just sufficient to sustain the essential organs in working condition, and may need extreme care in feeding, in quality and quantity, lest feeble vitality should be smothered and destroyed. But, if under these circumstances, with proper treatment in other respects, no effort is put forth by the nutritive organs to stay utter extinction of life, it may be regarded as inevitably a fatal case; for neither the incitement nor power to effort in this direction can be increased by artificial means."--Philosophy of Human Life, pp. 57-59 (Italics, mine. Author).
The process of nourishing the weary and hungry laborers of the body is not as simple as Jennings describes it, but it must be understood that nothing was known of the process of autolysis at the time he wrote. It will be recalled that Graham also described the process in much the same way as did Jennings. Indeed, as the two men were friends and more than once discussed such matters, it may be that they arrived at a common understanding of how the nourishment of the vital tissues was accomplished during periods of abstinence. In its general outline, however, Jennings' explanation of the way in which the body makes use of fasting in order to better achieve certain ends, is correct.
Sylvester Graham explained that when more food is used by the body than is daily supplied, "it is a general law of the vital economy" that "the decomposing absorbents always first lay hold of and remove those substances which are of least use to the economy; and hence, all morbid accumulations, such as wens, tumors, abscesses, etc., are rapidly diminished and often wholly removed under severe and protracted abstinence and fasting."
Recording another case, Jennings declares: "There has been no nourishment taken into the stomach for a number of days, and none will be taken for a number of days to come, for it would be a waste of power to compel the nutritive apparatus to work up raw material under present circumstances, if this could be done."--Philosophy of Human Life, p. 166.
This principle is susceptible of a wide application. Its workings are particularly apparent in the fast. The fasting body is very careful to hoard its materials, but rapidly absorbs and either eliminates or utilizes the materials contained in growths, deposits, effusions, swellings, etc.