424 Studies in Water Drinking [April-July 



is split off and the sodium salt of Phenolphthalein results. This 

 sodium salt then exerts its irritant action and purgation ensues. 

 Consider the complex organic molecule we call lecithin : it occurs in 

 animal and vegetable cells; is present as an important constituent 

 of brain and nerve tissue, in addition to being present in varying 

 proportions in many of the fluids and secretions of the human body; 

 and has been said to be related importantly to the problem of growth. 

 One of the lecithins, the so-called di-stearyl lecithin, bears the for- 

 mula C44H90NPO9, which shows it possesses a complex structure. 

 Yet water easily reduces it to its lowest terms. In other words the 

 addition of 4 molecules of water causes this complex lecithin mole- 

 cule to disintegrate ; and we have, as fragments, 2 molecules of 

 stearic acid, and one molecule each of glycerol, cholin and phosphoric 

 acid. Water was the magic key which unlocked the complex lecithin 

 molecule and enabled us to read its internal structure. 



In other chemical connections water is the keystone of the 

 molecular arch, and its removal is accompanied by the destruction of 

 the molecule. 



A good illustration of many of the important relationships of 

 water is afforded by the life history of protein, from its ingestion to 

 the excretion of its waste residues. We know that proteins are 

 absolutely essential to the proper nourishment of the human body. 

 In practically all f orms in which they are ingested by man they con- 

 tain water. When they reach the stomach they come in contact 

 with the gastric juice which is 98 per cent. water. They are there 

 acted on by pepsin, a proteolytic enzyme which causes the protein 

 molecule to take on water and break down into substances of a 

 simpler structure than the original protein. These protein cleav- 

 age products are then carried into the intestine where the acid of 

 the gastric juice is neutralized by the sodium carbonate present in 

 the aqueous Solution we term the pancreatic juice, water being 

 formed in the process of neutralization. The enzyme trypsin of the 

 alkaline pancreatic secretion then acts upon the protein cleavage 

 products, adds water to their structure and splits them into still 

 simpler substances. The intestinal juice, which is 98 per cent. water 

 now lends its assistance and the enzyme erepsin of this secretion aids 

 by a hydrolytic process in the production of the final cleavage prod- 



