120 PHYSIOLOGY OF ORGANIC LIFE. 



which he himself had paved, of discovering the 

 relation which the blood bears to the organs ; 

 and at once blasted the fair prospect which he 

 had opened to our view, of seeing the nature 

 and design of secretion ; instead of which the 

 process of secretion, so important and exten- 

 sive in the living system, is acknowledged by 

 all to be involved in utter darkness. 



Our ignorance of secretion appears to me, in 

 a great measure, to arise from mistaking the 

 relation which the blood bears to the organs by 

 the energy of which it is acted upon and chang-r 

 ed ; instead of considering blood as the passive 

 recipient, as thesubject matter to be acted upon, 

 not only by the vessel in which it is contained, 

 but by the organ in which it is deposited ; it is to 

 the stimulus of the blood, more than to its apti- 

 tude to be acted upon by the organs of secretion, 

 that the changes which it undergoes are referred. 



The relation which subsists between the mat- 

 ter from without, and the digestive organs 

 within, is precisely the same, in kind, as that 

 which subsists between the blood and the vari^ 

 ous parts to which it is conveyed. While the 

 digestive organs unify and assimilate different 

 species of matter to one, and the same kind, and 

 which afterwards subsists in the form of blood ; 

 the different secretory organs, on the contrary, 

 have the power to convert this blood into fluids 

 and solids, in their nature totally different ; as 



