FATS. 255 



the blood ; we need only observe the chyle when the food has been 

 of a fatty character, to convince ourselves, by the presence of fat- 

 vesicles, that it has been converted into a perfect emulsion, whilst 

 it will present only a slight turbidity from the presence of lymph- 

 or colourless blood-corpuscles, when the food has contained but 

 little fat. Boussingault* even succeeded, by a series of ingenious 

 experiments, in showing that only certain quantities of fat passed 

 in a given time from the intestinal canal into the general system, 

 and that the excess of fat was discharged unchanged with the excre- 

 ments. Thus he observed in the case of ducks, that a duck, when 

 kept on the fattest food, could not assimilate more than 19'2 gram- 

 mes of fat in twenty-four hours (or 0'8 of a gramme in one hour), 

 from the primes vice. 



A sharp contest has been obstinately maintained during the last 

 ten years in reference to the question whether the animal organism 

 does not possess the capacity of generating the requisite quantity of 

 fat from other nutrient substances besides preformed fat. Dumas, 

 Boussingault,t and some other French enquirers,! have endea- 

 voured to show by direct experiments, that herbivorous animals 

 take up sufficient fat with their food, and that the animal organism 

 has therefore no need of generating fat; while Liebig and his 

 school have arrived at a totally different conclusion from observa- 

 tions of a precisely similar character. For as they found that cer- 

 tain animals contained more fat, and discharged a larger quantity 

 in their milk and excrements, than they had obtained by their 

 food, they were led to the conclusion that the animal body must 

 possess the property of forming fat from other organic substances. 

 The contested point unfortunately long remained undecided, since 

 the two parties differed in their idea of that which they termed fat 

 in the food ; the French enquirers regarding as fats all the matters 

 that can be extracted from plants by ether, and Liebig reasonably 

 enough considering those matters only as fats which possessed all 

 other properties of fats besides that of solubility in ether. Liebig 

 appealed in support of his views to the experiments first made by 

 Huber, and afterwards repeated by Gundelach, and which appeared 

 to prove that bees, when fed on pure sugar, are capable of gene- 

 rating wax. Subsequently, Dumas, in conjunction with Milne 



* Ann. de Chim. et de Phys. 3 Se'r. T. 19, pp. 117-125, et T. 25, pp. 730-733. 

 f Ibid. T. J2,p. 153. 



$ Persoz, in Compt. rend. T. 18, p. 245 ; Payen and Gasparin, in Compt. 

 rend. T. 18, p. 797 ; Letellier, in Ann. de Chim. et de Phys. 3 Se'r. T. 11, p. 433. 

 Pkyfair, in Phil. Mag. Vol. 22, p. 281. 



