108 ANIMAL FUNCTIONS. 



cle of the chyle, and from which there proceeds a tube t, 

 called the thoracic duct, which conveys the chyle to the 

 circulation. I, is a portion of the liver. That portion of 

 the heart h, which is marked u, is called the auricle, 

 while the cavity h, is called the ventricle, a, is the aorta, 

 which is the trunk of the largest artery, and v, v,v, are the 

 large veins which convey the blood "to the heart. The 

 part b, is a portion of the lungs. 



Having pointed out the different parts, we will next 

 explain in few words, the different processes by which 

 food is changed into blood, and also the course of the 

 blood in its circulation. 



The food being masticated, and mixed with the fluid 

 secretions of the mouth, is then collected into a mass by 

 the muscles of the cheeks and tongue, and swallowed, 

 being carried along the tube o by its contractions,<lown 

 to the stomach s. There it is mixed with a fluid secre- 

 tion of the stomach, called the gastric juice, and by which 

 it is dissolved, and prepared to afford chyle after it has 

 been conducted through the pylorus. After having pas- 

 sed the pylorus p, the food is mixed with the bile, a bit- 

 ter secretion from the liver, and also with a fluid from 

 the pancreas, when a portion is elaborated into chyle, 

 and is ready for absorption into the lacteals, which are 

 the vessels spread over the mesentery, like a net work, 

 as shown by the figure. 



The chyle being taken up by the lacteals, the mouths 

 of which are thickly spread over the interior of the in- 

 testinal tube, is carried by many branches to the recep- 

 tacle of the chyle r, from which it is conveyed by the 

 thoracie duct, t, to one of the large veins under the arm, 

 called the subclavian vein, and by this vein to the heart. 

 It thus gains admittance to the general circulation of the 

 blood, and by a process which we cannot explain, be- 

 comes blood itself. 



It is by means of a constant reception of chyle into the 

 circulation, that the quantity of blood continues undimin- 

 ished ; and that the arteries are enabled to furnish the 



Explain Fig. 74, and point out the name and situation of each part, as 

 designated by the letters. In what part of the system is the chyle thrown 

 into the circulation 7 



