SECRETION. 345 



various textures and substances which compose 

 all the parts of the animal frame. All the modifi- 

 cations of cellular substance, in its various states 

 of condensation ; the membranes, the ligaments, 

 the cartilages, the bones, the marrow ; the mus- 

 cles, with their tendons ; the lubricating fluid of 

 the joints ; the medullary pulp of the brain ; the 

 transparent jelly of the eye ; in a word, all the 

 diversified textures of the various organs, which 

 are calculated for such different offices, are 

 derived from the same nutrient fluid, and may 

 be considered as being merely modified arrange- 

 ments of the same ultimate chemical elements. 



In what, then, we naturally ask, consists 

 this subtle chemistry of life, by which nature 

 effects these multifarious changes ; and in what 

 secret recesses of the living frame has she con- 

 structed the refined laboratory in which she 

 operates her marvellous transformations, far sur- 

 passing even those which the most visionary 

 alchemist of former times had ever dreamed of 

 achieving? Questions like these can be fairly 

 met only by the confession of profound igno- 

 rance ; for, although the subject of secretion has 

 long excited the most ardent curiosity of physi- 

 ologists, and has been prosecuted with extraor- 

 dinary zeal and perseverance, scarcely any 

 positive information has resulted from their 

 labours ; and the real nature of the process 



