444 NUTRITION. 



Finally, Boussingault* found by experiments on pigs that (to 

 take an example) eight-months' pigs contained far more fat than 

 had existed in their food, but that when they were fed solely on 

 potatoes there was no more fat accumulated in them in the course 

 of six months than corresponded to the amount of fat contained 

 in the potatoes which they consumed ; and that such kinds of 

 food as potatoes, which could not of themselves be applied to the 

 formation of fat within the body, acquired this property by a 

 slight addition of fat or of albuminous matters. 



In our previous notice of the quantitative metamorphosis of 

 matter we have not done more than draw the balance between the 

 ingesta and the egesta which we have observed in the living 

 animal organism under various physiological conditions. It has 

 been objected against this method, that it affords us no light 

 whatever in reference to the interchange of the organic elements 

 within the body in the process of nutrition ; but independently of 

 the fact that this is the only path we are able to pursue in order 

 to obtain a general view, it has also led us to a number of facts 

 which enable us to gain an insight into the intermediate stages of 

 molecular motions in the body. It cannot, however, be denied 

 that, notwithstanding many of the conclusions yielded by this 

 method, we are still so ignorant of the intermediate metamorphosis 

 of matter, that we can only adduce the facts known in reference 

 to this subject, as mere appendages to our previous remarks. 

 While we have endeavoured throughout the whole course of this 

 work to notice all the important relations of each substance 

 substratum, fluid, and tissue in reference to the metamorphosis of 

 matter, we have always directed our fullest attention to this sub- 

 ject, which we regard as the crowning point of physiological 

 chemistry, and the advance made in science during the last few 

 years has indeed yielded the most extraordinary results in this 

 respect. Notwithstanding many obvious deficiences and numerous 

 imperfections, we see revealed before our eyes the image of a life 

 rich in internal relations and external forms, and alike inex- 

 haustible in the multiplicity of its phenomena and the incentives 

 to future investigations. But still it is only a mere picture, in 

 which many results of vegetative life are undoubtedly represented 

 in too ideal a form ; for whilst all phenomena are only parts of a 

 motion regulated by definite laws, many portions of this sketch 

 are drawn in false perspective. To find the correct perspective, 

 we require to make a certain number of direct measurements, 

 * Compt. rend. T. 20, p. 1726. 



