78 PHOSPHATES ABOUND IN 



consume force merely in order to supply matter for 

 respiration. 



Cultivation is the economy of force. Science 

 teaches us the simplest means of obtaining the 

 greatest effect with the smallest expenditure of 

 power, and with given means to produce a maxi- 

 mum of force. The unprofitable exertion of power, 

 the waste of force in agriculture, in other branches 

 of industry, in science, or in social economy, is 

 characteristic of the savage state, or of the want of 

 cultivation. 



XV. A comparison of the urine of the carnivora 

 with that of the graminivora shews very clearly, that 

 the process of metamorphosis in the tissues is differ- 

 ent, both in form and in rapidity, in the two classes 

 of animals. 



The urine of carnivorous animals is acid, and 

 contains alkaline bases united with uric, phosphoric, 

 and sulphuric acids. We know perfectly the source 

 of the two latter acids. All the tissues, with the 

 exception of cellular tissue and membrane, contain 

 phosphoric acid and sulphur, which latter element 

 is converted into sulphuric acid by the oxygen of 

 the arterial blood. In the various fluids of the 

 body there are only traces of phosphates or sul- 

 phates, except in the urine, where both are found 

 in abundance. It is plain that they are derived 

 from the metamorphosed tissues ; they enter into 

 the venous blood in the form of soluble salts, and 



