METABOLISM 221 



starvation, replacing a portion of the normal creatinine. A most 

 interesting fact is that all tissues and organs do not lose weight 

 in like amount as starvation proceeds. Organs of vital impor- 

 tance such as the heart, the brain and nerves are preserved prac- 

 tically without loss of weight, whereas the skeletal muscles, the 

 liver (loses glycogen) and adipose tissue lose a very considerable 

 portion of their weight. The body tries to save the most vitally 

 important organs, and does so at the expense of less indispen- 

 sable tissues, which are called upon to furnish fuel and undoubt- 

 edly also repair material for the vital parts. 



The nitrogen excretion of a fasting animal gradually de- 

 creases as time goes on, probably as a result of the decreased 

 amount of protein tissue in the body. Shortly before the death 

 of the animal the nitrogen excretion rises sharply. This is known 

 as the pre-mortal rise. It appears as if the organism gives up 

 the struggle to protect its tissues from destruction and that the 

 overtaxed organism begins to give way. After a prolonged fast, 

 the total nitrogen excretion in man falls to the neighborhood of 

 about 2 grams per day. This appears to be the minimum, and 

 has been taken by some to represent the actual necessary wear 

 and tear of the protein tissues of the body. Possibly, however, it 

 is necessary for the body to break down the protein which this 

 represents in order to obtain some particular amino acid or 

 acids needed in the synthesis of some absolutely essential prod- 

 uct of internal secretion. 



Several cases are on record, and the author himself has known 

 individuals who have derived great benefit from an occasional 

 wisely timed fast. The digestive and excretory organs are given 

 a rest, the tissues are cleared of all unnecessary stored up ma- 

 terial, and the body undergoes a thorough housecleaning. 



Unknown Food Constituents. Vitamins. Until recently it 

 was believed that if an individual were supplied with enough 

 protein, the necessary salts, and amounts of carbohydrates and 

 fats sufficient to make up the total of energy required, that his 

 diet was adequately regulated. Recent developments have 

 shown that this list is incomplete, and that certain substances 



