94 CYCLOSES, CHOLESTEROL AND CHOLIC ACID 



It is questionable whether animal tissues are able to accomplish the 

 synthesis of any of these substances; in fact all the evidence at present 

 available contributes to show that they cannot, and that we are 

 absolutely dependent upon vegetable tissues for our supplies of these 

 very essential materials. The investigations of Gardner, Denis 

 Chalatov and Anistchakov have shown that addition of cholesterol to 

 the dietary in abnormal amounts, increases the cholesterol-content qf 

 the tissues, while a diet extremely deficient in cholesterol-results in a 

 like deficiency of cholesterol in the blood and tissues. On the other 

 hand, in vegetable tissues terpenes and terpene-derivatives abound so 

 that the ultimate source of cholesterol in the diet w^ould appear to 

 reside in these products of the synthetic activity of plants. 



The power of the animal organism to destroy cholesterol is very 

 limited, and if a considerable excess be administered in the diet, the 

 unutilized cholesterol is stored away in various tissues, particularly 

 in the liver, spleen and suprarenal bodies. In certain animals, for 

 example rabbits, but not in others, the excess of cholesterol is in part 

 deposited in the interior of the arterial walls, leading to the formation 

 of lesions, which simulate arteriosclerotic lesions of the arteries in 

 human beings. The normal channel of excretion of cholesterol would 

 appear to be the bile, in which it is present in part in the form of unal- 

 tered cholesterol, and in part in the form of cholic acid, combined with 

 amino-acetic acid or amino-ethyl-sulphonic acid to form the "bile- 

 acids." Both of these substances are in part reabsorbed from the 

 intestine, so that there is a tendency for cholesterol and its products 

 to circulate in the body, and accumulate in the tissues. Of course this 

 process cannot go on unchecked, otherwise the accumulations of 

 cholesterol in the tissues would soon extinguish their functional 

 activities. It appears possible from the abundance of cholesterol 

 esters in the suprarenal cortex, particularly during cholesterol over- 

 feeding, that the suprarenal glands may play a part in assisting to 

 eliminate or destroy cholesterol, but regarding the nature of the 

 ultimate products which may be formed in this process we are entirely 

 in the dark. Inosite, on the other hand, which contains within itself 

 a much higher proportion of oxygen than cholesterol, is partially 

 oxidized by animal tissues and the products of its oxidation appear to 

 be indistinguishable from those of carbohydrate-metabolism. 



Not even inosite, however, and still less cholesterol are of importance 

 from the purely nutritive aspect, i. e., as sources of energy. The 

 calorific value of the hydro-aromatic fraction of the diet is so small as 

 to be negligible in comparison with the total. Their significance lies 

 elsewhere, and if we revert to the analogy of inanimate machines we 

 must class them with the lubricants and other accessory substances 

 which are essential to the smooth running of the machine, rather than 

 with the fuel which supplies the energy of the machine. Indirectly, 

 indeed, they must contribute to the available energy-value of the diet 

 by permitting its more efficient consumption, just as the judicious 



