E. Voit2 has prepared the following table from an experiment of Schondorff3 upon a fasting dog. The quotient N content/ Fat content give the ratio between these two components of the organism at the time specified. The ratio Energy protein/Energy total gives the percentage of the total energy derived from the protein metabolism. The dog died on the thirty-eighth day of his fast:

1 E. Voit: "Zeitschrift fur Biologie," 1901, xli, 545.

2 E. Voit: Ibid., p. 520.

3 SchSndorff: "Pfluger's Archiv," 1897, Ixvii, 430.

Protein Metabolism In Starvation As Influenced By The Fat Content Of The Animal

E. Voit finds that the amount of protein metabolism depends so absolutely upon the relation between the amount of fat and protein in the body (the N content/ Fat content) that, knowing this ratio, he says he can estimate the relative protein metabolism. When the ratio rises to 4.84 in the rabbit, then 98.3 per cent, of the total energy may be derived from protein. Had fat still been present in considerable quantity the protein metabolism would have remained low. This is the law which governs the gradual rise in the protein metabolism during starvation, the "premortal rise" it has been termed. The increased combustion of the protein is due to the requirement for energy in an organism which has a constantly decreasing amount of fat upon which to draw:

Zuntz1 describes a dog which lived in a constant state of undernutrition for about a year. The energy requirement was as follows:

Though the nitrogen in the urine was not collected, Zuntz considers it possible that with the utilization of body fat the metabolism of protein increased, and therefore the heat production increased (see p. 238) toward the end of life.

1Zuntz: "Biochem. Zeitschr.," 1913, lv, 341.

The actual loss of body weight is greater when protein is the source of energy than when the energy is derived from fat.

The metabolism of protein in 100 grams of flesh yields only 80 calories in contrast with 930 calories liberated when 100 grams of fat are oxidized. To obtain equivalent amounts of energy there must, therefore, be a destruction of eleven and a half times more "flesh" by weight than fat.

Rubner1 has maintained a dog for a long period on a diet of fat which was sufficient in amount to cover the energy requirement. The content of body nitrogen fell from 358.3 grams to 166 grams, a loss of 53.7 per cent. Rubner finds that during the whole period the daily waste of nitrogen is 0.9 gram per 100 grams contained in the body. This "wear and tear" quota is therefore a function of the intensity of the life processes, being proportional to the amount of protoplasmic material present.

What is the cause of death from starvation? It does not seem to be due to an essential change in the composition of the cells themselves, for no chemical alteration has been detected in them.2 What, then, is the cause of death? The general argument of E. Voit is as follows: It must be due either to a general failure of all the cells or injury of certain organs which are necessary for life. If the first cause were the true one, then death would take place when a certain definite percentage of protein loss occurred. This does not happen, since the body loss at the time of death may vary between 20 and 50 per cent, of its original protein content. When the genital organs of the salmon develop at the expense of the liquefying muscle substance brought them by the blood, not a single muscle cell of the fish is killed, even though these lose 55 per cent, of their protein in the process (Miescher). It seems extremely improbable, then, that a much smaller loss of protein in starvation can be the cause of general cellular death. On the other hand, if death be due to the failure of certain organs especially important to life, the cause is to be found in two factors:

1 Rubner: "Archiv fur Hygiene," 1908, lxvi, 49.

2 Abderhalden, Bergell, and Doerpinghaus: "Zeitschrift fur physiologische Chemie," 1904, xli, 153.

Either these organs receive too little nutrition for their proper functioning, or they become so emaciated that they fail in spite of sufficient nutriment. Either the fuel is insufficient or the machine wears out.

The following table gives some answer to this. The general arrangement is in the order of the greater original fat content of the animals:

Influence Of Fat Content On Protein Metabolism And On Length Of Life In Starvation

In the first three animals a large amount of fat was present at the time of death, and this had prevented a great tissue waste. Abundant food was therefore available for the cells. The cause of death seems, therefore, to be due to a reduction of activity in one or more organs important for life.

Again, if the protein loss be kept down by administering protein in quantity insufficient for the heating demands of the organism, the animal is kept living largely on his own fat. Schulz1 in this way kept two dogs alive for twenty.eight and thirty-eight days, with losses of body nitrogen amounting to only 18 and 7 per cent, of the original quantity. The fat present was only 0.4 to 0.5 per cent, at the end. These dogs certainly suffered from no general loss of cell tissue. E. Voit concludes that death from starvation is primarily due to loss of substance in organs important to life, but it may also ensue under certain circumstances as a result of deficient nutrition to these organs.

1 Schulz: "Pfluger's Archiv," 1899, lxxvi, 379.

Schulz1 and his pupils let a dog which was fat and well nourished fast for twenty-seven days. On the twenty-fifth day the animal manifested weakness, which, on the twenty-seventh day, appeared to threaten its life. Then for a day 400 c.c. of milk were given to the dog and on four subsequent days 300 grams of meat each day. Although these quantities of food were greatly under the quantity required to maintain the dog without loss of body fat, still the animal recovered its strength, added 7.3 grams of protein nitrogen to its body, and then lived during a second period of sixty-one days of starvation. During this second fasting period the protein metabolism was on a much lower level than during the first period. Schulz notices that when the fasting dog still contains considerable fat, protein in the food is readily retained, even though the content of energy ingested be under the body's needs. When, however, the body fat is nearly exhausted, all the ingested protein and some body protein besides is destroyed to provide for the support of the organism. Schulz concluded that death from starvation is due to autotoxemia, a condition which was relieved in the fasting experiment mentioned above by the ingestion of meat.