174 ABSORPTION. 



system ; and, finally, when the whole of the fat has been disposed 

 of by the nutritive processes, the serum again becomes transparent, 

 and the blood returns to its ordinary condition. 



In this manner the nutritive elements of the food, prepared for 

 absorption by the digestive process, are taken up into the circulation 

 under the different forms of albuminose, sugar, and chyle, and accu- 

 mulate as such, at certain times, in the blood. But these conditions 

 are only temporary, or transitional. The nutritive materials soon 

 pass, by catalytic transformation, into other forms, and become 

 assimilated to the pre-existing elements of the circulating fluid. 

 Thus they accomplish finally the whole object of digestion ; which 

 is to replenish the blood by a supply of new materials from without. 

 There are, however, two other intermediate processes, taking place 

 partly in the liver and partly in the intestine, at about the same 

 time, and having for their object the final preparation and perfec- 

 tion of the circulating fluid. These two processes require to be 

 studied, before we can pass on to the particular description of the 

 blood itself. They are : 1st, the secretion and reabsorption of the 

 bile ; and 2d, the production of sugar in the liver, and its subse- 

 quent decomposition in the blood. 



