4^ Theory of the Nutrition [BOOK in. 



the harder parts. But if the latter again absorb water, and the 

 forces of repulsion consequently gain the preponderance, then 

 the consistence of the vegetable parts is dissolved, and this 

 decomposition restores to them the power of forming new 

 vegetable products ; therefore the stock of nutritive substance 

 in nature can never be exhausted ; this stock is the same in 

 animals and plants, and is fitted by a small change of texture 

 to feed the one or the other. 



He goes on to say, that it results from his experiments, that 

 leaves are very useful for the nourishing of the plant, inasmuch 

 as they draw up the food from the earth ; but they seem also 

 to be adapted to other noble and important services; they 

 remove the superfluous water by evaporation, retaining the 

 parts of it that are nutritious, while they also absorb salt, nitre, 

 and the like substances, and dew, and rain ; and since, like 

 Newton, he regarded light as a substance, he concludes by 

 asking : ' may not light, which makes its way into the outer 

 surfaces of leaves and flowers, contribute much to the refining 

 of the substances in the plant ? ' 



It might be gathered from these expressions that Hales 

 attributed importance for purposes of nutrition only to the 

 substances suspended in the air ; but this was not the case ; 

 for we read in the 6th chapter, that he had proved by 

 experiment that a quantity of true permanently elastic air is 

 obtained from vegetable and animal bodies by fermentation 

 and dissolution (dry distillation) ; the air is to a great extent 

 immediately and firmly incorporated with the substance of 

 these bodies, and it follows therefore that a large quantity of 

 elastic air must be constantly used in forming them. 



But Hales not only regards the air as a nourishing 

 substance, but he sees also in its elasticity, which counteracts 

 the attraction of other substances, the origin of the force 

 which maintains the internal movements in the plant. He 

 says that if all matter were endowed only with forces of 

 attraction, all nature would at once contract into an inactive 



