AND THE LOWER ANIMALS. 3 



of our organs represent collectively the wheels, tubes, 

 pistons, &c. The machine receives but the coal and 

 the water ; it carries its grate with it, and prepares, 

 without the direct assistance of the artisan, the steam 

 required to set the apparatus in motion ; similarly, say 

 the mechanical physiologists, our body receives every 

 day its supply of solids and liquids ; it burns a por- 

 tion of these substances to maintain the animal heat, 

 and with the rest it builds up the organs which require 

 it, and supplies the liquids necessary to put the whole 

 in working order. In us, moreover, as in the loco- 

 motive, the solid matter once fixed, undergoes no 

 change, or at the most is eventually worn out. The 

 materials expended, and which must be re-supplied 

 — the coal and water, the food and drink — are con- 

 verted in the machine into smoke and steam, in man 

 into steam (vapour) also, and into various secretions. 



This theory we see, leaps over the difficulties which 

 are presented by the history of development ; it is 

 framed for an organism fully formed and performing 

 all its functions. But then, does it stand the test of 

 application, and does it account for the facts with 

 which the maintenance and decay of organisms supply 

 us ? Certainly not, at least in the animal kingdom. 



In the adult and in the aged, numerous normal and 

 pathological phenomena demonstrate the constant 

 change of the solid, as well as of the liquid consti- 

 tuents. The now antiquated experiments of Duhamel, 

 so ingeniously begun and carried out by M. Mourens, 

 and the works of M. Chossat, leave no room for doubt 

 on this point. The latter, among others, fed poultry 

 and pigeons upon food from which he had removed 

 the calcareous salts only. Thus he supplied these 



b2 



