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A TEXTBOOK OF PHYSIOLOGY 



oil contained in oats. The wild-boar, when feeding on acorns and 

 beech-nuts, acquires a fat with properties akin to those of the beech 

 and acorn oils. Many exact experiments have also been made to 

 prove this point. An animal is starved to reduce its fat as much as 

 possible, and it is then fed with a fat the properties of which, such 

 as melting-point, iodine number, etc., are known. In addition, the 

 fatty acid contained in the fat often has its own characteristic 

 properties. Such fats are rapeseed oil, linseed oil, sesame oil, coco- 

 butter, etc. After feeding a starved dog or goose with sesame oil, 

 it was found that the fat was more oily, and the presence of the sesame 

 oil could be demonstrated in the fat by shaking it with an equal volume 

 of strong hydrochloric acid and a trace of a 2 per cent, alcoholic solu- 

 tion of furfurol. A purple-red colour developed when sesame oil 

 was present. The following figures show the effect of feeding mutton 

 fat and of feeding coco -butter on dogs : 



The fed fat also goes in part into the milk, so that the iodine number 

 and other properties of the cream are altered. The characteristic test 

 for sesame oil is given by the cream yielded by a cow fed with 

 sesame oil. It is probably of considerable importance that the right 

 fat should be stored in order that the body may be kept hard and 

 in good condition. The soft townsman may owe his softness to the 

 quality of his fat as well as to lack of muscular development. 



Fat from Carbohydrate. Fat may also arise from the carbohydrate 

 taken in as food. This is obvious to those engaged in fattening pigs 

 or geese for market. Carbohydrate is the chief food given. It has 

 been proved scientifically by giving animals, after preliminary starva- 

 tion, a diet containing a minimum of protein and much carbohydrate. 

 By comparing these with controls e.g., animals taken from the 

 same litter it can be shown that the experimental animals put on 

 so much fat that even if it be supposed that all the non-nitrogenous 

 moiety of the protein eaten were converted into fat, yet there is 

 more fat to be accounted for; this must have come from the carbo- 

 hydrate fed. 



Evidence in favour ef the formation of fat from carbohydrate is 

 also obtained from the respiratory quotient (1) of hibernating 

 animals which are storing fat preparatory to their winter sleep, (2) of 

 animals which are being fattened by forced feeding with large amounts 

 of carbohydrate for example, of geese stuffed to make fat livers 

 for the preparation of pdte de foie gras. Under these circumstances, 



