126 



We cannot sufficiently admire the prodigious apparatus 

 of vessels which perform the secretions of different kinds. 

 The kidneys, the liver, the pancreas, &c. are labyrinths 

 in \vhich the most consummate anatomist is bewildered. 

 We can only discover an inconceivable mass of white tubes, 

 of an extreme minuteness, folded together in thousands 

 of different ways, which do not admit of any injection, 

 through adhering to the blood-vessels, and being placed 

 end to end by imagination, would have formed a chain 

 of several leagues in length. This is all that: art has dis- 

 covered in the secretory organs. But what a number of 

 interesting particulars do these minute, hollow eviinders 

 contain, which have escaped our notice and instruments ! 

 What varieties should we not discover in their ttruchire, 

 functions, and exercise, were ue permitted to descend to 

 the bottom of this abyss, which conceals from us one of 

 the greatest mysteries of nature ! All the animal liquors 

 are more or less mixed, and these smn.ll tubes no doubt 

 sufficiently diversify themselves to separate the various 

 mofecules that must necessarily enter into the composi- 

 tion of every liquor. What then must be the structure 

 and fineness of those that filtre this so subtle fluid, coin- 

 pared to ether or light, whose operations are diversi- 

 fied almost to infinity ! 



7. If we knew how a single fibre grows, we could 

 tell how the animal grows ; for his whole body is only 

 an assemblage of fibres differently formed and combined. 

 Growth always operates by-mitrition. This incorporates 

 into the fibre molecules of an heterogeneous nature, 

 which extend in every part. The fibre incorporates 

 into itself the heterogeneous molecules, according to its 

 own nature. A fibre is not itself composed of other 

 fibres : these of still other fibres : of which there would be 

 no end. Br.t the fibres is formed of molecules or elements, 

 M'liose nature, proportions, and arrangement, respec- 

 tively determine the species of the frbre, and adapt it to 

 such or such a function. Thus the elements of the fibre 

 ultimately effect assimilation, which, by uniting with the 

 .nutritious molecules, that have an affinity with then), 



e them at the same time an arrangement like that 



