HEALTH AND DISEASE 



in the abdomen at the root of the mesentery, whilst those connected 

 with the lymphatics are found in the axilla, groin, neck, thorax, &c. 

 The purpose of the lacteals, which have their origin in the intestine, is 

 to absorb or take up the constituents of the 

 food, in which they are assisted by the blood- 

 vessels, whilst the lymphatics, which are 

 everywhere distributed through the tissues 

 of the body, reconduct to the larger blood- 

 vessels the plasma of the blood which, having 

 passed through the walls of the smaller blood- 

 vessels, is in excess of the requirement of the 

 tissues, and contains some of the products of 

 their disintegration. As there are some dif- 

 ferences between the lacteal and lymphatic 

 vessels it will be expedient to describe them 

 separately, though it must be borne in mind 

 that they are only parts of the same system. 



The Lacteal System.— It is justifiable 



in common parlance to say, when an animal 

 has eaten a hearty meal, that it has got its 

 food inside it, but from a physiological point 

 of view the food is still in reality outside 

 the body, and no matter what quantity has 

 been ingested it is unavailable for the nutri- 

 tion of the tissues, or the production of heat 

 or of nervo-muscular force, until it has been 

 absorbed and assimilated. The starches, oils, 

 and proteids which form the staple of the 

 typical foods such as oats, barley, wheat, 

 and other cereals are, in the raw state, in- 

 capable of passing through the walls of the 

 intestine. In order that they may do so it 

 is necessary that they should be rendered 

 soluble, and this duty devolves on the 

 various digestive secretions, that we have 

 seen are poured forth from the numerous 

 glands connected with the alimentary canal. 

 By these juices starches are converted into sugars, oils into very fine 

 emulsions or into soaps, and proteids into peptones, being in each case 

 so modified that they are rendered capable of permeating the intestinal 

 walls and the vessels ramifying upon them, and thus truly entering 



Fig. 181. — Sketch of the Lymphatic Vessels 

 of the Fore-Leg (inner aspect) 



