358 STUDIES IN ADVANCED PHYSIOLOGY. 



changed into that peculiar form of fat characteristic of the 

 animal which has eaten it. In the human body these dust 

 particles of fat in the lacteal are now no longer butter and 

 lard, but are human fat. As with so many other things we 

 still have no knowledge of the manner in which this chemi- 

 cal change is effected. It may be in place to call attention 

 to the fact that but little fat reaches the blood vessels. 

 Practically all of it is carried by the lacteal. These vessels 

 owe their name to the circumstance that after a meal they 

 are usually filled with a white milky substance, the particles 

 of fat in question. It was formerly believed that they ab- 

 sorbed all the food, and so were erroneously called absorb- 

 ents. We know that the proteids, and the sugars, and the 

 albumens are carried by the portal circulation to the liver. 



It has been pointed out by some physiologists that pos- 

 sibly the involuntary muscular tissue found in the villi of 

 the intestine produces a kind of contraction and expansion 

 of each villus, and so the central lacteal is enabled to suck 

 or force the fat into itself. These contractions of the villi, 

 they hold, may be due to the stimulation caused by the bile, 

 and in this way they explain the observed fact that bile 

 seems to aid in the absorption of fats. Through these lac- 

 teals the fat is carried towards ,the thoracic duct, and by 

 this poured into the left subclavian vein and so distributed 

 by the circulation. The further changes which this fat 

 undergoes will be discussed later. 



The various salts, the water and the albuminoids in the 

 form of gelatin, present no difficulties in their absorption 

 and need not be further treated. 



When finally all foods have been absorbed the following 

 is the state of things : 



First. The peptones changed back into the albumens 

 are carried by the portal circulation to the liver. 



Second. All the sugars changed into dextrose, are also 

 carried by the portal circulation to the liver. 



Third. The various salts and the water drop into the 

 portal circulation largely; possibly, also, the soluble soaps, 

 the glycerine and the albuminoids. 



