CHAPTER XT. 



ABSORPTION. 



General considerations Absorption by blood-vessels Absorption by lacteal and 

 lymphatic vessels Physiological anatomy of the lacteal and lymphatic sys- 

 tem Thoracic duct Structure of the lacteal and lymphatic vessels Lym- 

 phatic glands Absorption of albuminoids by the lacteals Absorption of 

 glucose and salts by the lacteals Absorption of water by the lacteals Ab- 

 sorption from parts not connected with the digestive system Absorption 

 from the skin Absorption from the respiratory surface Absorption from 

 closed cavities, reservoirs of glands, etc. Absorption of fats and insoluble 

 substances Variations and modifications of absorption Influence of the 

 condition of the blood and the vessels on absorption Influence of the ner- 

 vous system on absorption. 



DIGESTION has two great objects : one is to reduce the 

 different alimentary principles to a fluid condition, and the 

 other to commence the series of catalytic transformations by 

 which these principles are rendered capable of nourishing 

 the organism. The principles thus acted upon are taken 

 into the blood as fast as the requisite changes in their consti- 

 tution are effected ; and once received into the circulation, 

 become part of the great nutritive fluid, supplying the waste 

 which the constant regeneration of the tissues from materials 

 furnished by the blood necessarily involves. The only group 

 of principles which does not obey this general law is the 

 fats. Though a small portion of the fat taken as food passes 

 directly into the blood-vessels of the intestinal canal, by far 

 the greatest part finds its way into the circulation by means 

 of special absorbent vessels which empty into large veins. 

 In whatever way fat enters the blood, it is never dissolved, 

 but is reduced to the condition of a fine emulsion. 



