110 OF FOOD. 



within their reach, and would not touch it ; others tasted of it, but 

 would not eat ; others still devoured a certain quantity of it once 

 or twice, and then obstinately refused to make any further use of it." 



In one instance, however, Magendie succeeded in inducing a dog 

 to 'take a considerable quantity of pure fibrin daily throughout the 

 whole course of the experiment; but notwithstanding this, the 

 animal became emaciated like the others, and died at last with the 

 same symptoms of inanition. 



The alimentary substances of the second class, however, viz., the 

 sugars and the oils, have been sometimes thought less important 

 than the albuminous matters, because they do not enter so largely 

 or so permanently into the composition of the solid tissues. The 

 saccharine matters, when taken as food, cannot be traced farther 

 than the blood. They undergo already, in the circulating fluid, 

 some change by which their essential character is lost, and they 

 cannot be any longer recognized. The appearance of sugar in the 

 mammary gland and the milk is only exceptional, and does not 

 occur at all in the male subject. The fats are, it is true, very gene- 

 rally distributed throughout the body, but it is only in the brain 

 and nervous matter that they exist intimately united with the re- 

 maining ingredients of the tissues. Elsewhere, as already mention ed, 

 they are deposited in distinct drops and granules, and so long as 

 they remain in this condition must of course be inactive, so far as 

 regards any chemical nutritive process. In this condition they 

 seem to be held in reserve, ready to be absorbed by the blood, 

 whenever they may be required for the purposes of nutrition. On 

 being reabsorbed, however, as soon as they again enter the blood 

 or unite intimately with the substance of the tissues, they at once 

 change their condition and lose their former chemical constitution 

 and properties. 



It is for these reasons that the albuminoid matters have been 

 sometimes considered as the only "nutritious" substances, because 

 they alone constitute under their own form a great part of the 

 ingredients of the tissues, while the sugars and the oils rapidly dis- 

 appear by decomposition. It has even been assumed that the pro- 

 cess by which the sugar and the oils disappear is one of direct 

 combustion or oxidation, and that they are destined solely to be 

 consumed in this way, not to enter at all into the composition of 

 the tissues but only to maintain the heat of the body by an inces- 

 sant process of combustion in the blood. They have been therefore 

 termed the " combustible" or " heat-producing" elements, while the 



