76 HYDROCARBONACEOUS PROXIMATE PRINCIPLES. 



is no clonbt that fat is produced from starch and glucose in vegetables 

 during a certain period of their growth. The oily seeds of certain 

 plants while still immature contain starch ; but as they ripen, the starch 

 diminishes or disappears and oil takes its place. 1 



It is also a matter of common observation that articles of food, con- 

 sisting largely of starch or sugar, or of both, are especially apt to be 

 fattening, both for man and animals and in sugar growing countries, 

 during the short season occupied in extracting and preparing the sugar, 

 the horses and cattle, as well as the laborers emplo3 r ed on the plantation, 

 all of whom partake freely of the saccharine juices, grow remarkably 

 fat, and again lose their superabundant flesh when the season is past. 

 It is not known, however, whether the saccharine matters in these in- 

 stances are directly converted into fat, or whether they pass through a 

 series of intermediate changes which furnish the materials for its forma- 

 tion. The abundant accumulation of fat in certain regions of the body 

 and its absence in others, and more particularly its constant occurrence 

 in situations to which it could not have been transported by the blood, 

 as the interior of the cells of the costal cartilages, make it probable that 

 oily matter is often formed from the metamorphosis of other proximate 

 principles, upon the very spot where it makes its appearance in the 

 solid tissues. Cases of hereditary obesity, and of obesity occurring 

 only after a definite period of life, indicate also that the excessive depo- 

 sition of fat may be due to internal causes dependent on the special 

 condition of the bodily system. 



In the female during lactation, a large part of the oily matter intro- 

 duced with the food, or formed in the body, is discharged with the milk, 

 and goes to the support of the infant. But in the female in the inter- 

 vals of lactation, and in the male at all times, the oily matters almost 

 entirely disappear by decomposition in the interior of the body ; since 

 the small quantity which is discharged with the sebaceous matter by 

 the skin bears only an insignificant proportion to that which is intro- 

 duced daily with the food. 



Beside the fats proper there is also contained in the body the fol- 

 lowing substance, which resembles fat in the general features of its 

 chemical composition, and in some of its reactions, but differs from 

 them in three important particulars, namely : 1st, in being volatile at a 

 high temperature ; 2d, in exerting a rotatory action on polarized light ; 

 and 3d, in the fact that it cannot be transformed, by the action of alka- 

 line solutions, into glycerine and a fatty acid that is, it is not saponi- 

 fiable. 



Cholesterine, C 26 H 44 0, 



So called from its being often precipitated as a solid deposit from the 

 bile, in which form it was first discovered. Cholesterine is an ingredient 

 in the blood-plasma and the blood-globules, in the bile, in the sebaceous 



1 Prof. S. W. Johnson, How Crops Grow. New York, p. 94. 



