184 PHYSIOLOGY. 



panies it, first into the conglobate glands of the mesentery, and 

 from thence to the receptaculum chyli, as it is called. From 

 this the chyle passes by the thoracic duct into the left subcla- 

 vian vein. In one or other part of this course of the chyle, the 

 vessels carrying it are joined by lymphatics, returning the 

 lymph from almost every part of the body. 



CCXXI. The matters contained in the intestinal canal, not 

 taken into the lacteals, are moved onwards in the course of the 

 intestines, becoming by degrees of a thicker consistence, espe- 

 cially in the colon, where their motion is considerably retarded; 

 but, at length, they are moved onwards to the extremity of the 

 rectum, where their weight, bulk, and acrimony excite motions 

 which throw them entirely out of the body. 



CCXXI I. This is the course of the alimentary matters, so 

 far as they can be considered as any ways in a separate state. 

 Of the motions of the several organs concerned in this course, 

 we pass over those of manducation, deglutition, or others de- 

 pending on the action of muscles, the functions of which are 

 readily understood from a knowledge of their situation ; and 

 we are here to consider only the motions of the alimentary canal 

 itself. 



CCXXIII. The motions in the oesophagus depend upon 

 the action of its muscular fibres, which are chiefly those form- 

 ing a chain and circularly surrounding it. This tube, by the 

 morsel of food pushed into it by the action of deglutition, is 

 necessarily dilated, and its circular fibres are thereby excited to 

 a contraction. But as these fibres are successively dilated, so 

 they are also contracted, and push on their contents through 

 the several portions of the tube, alternately and successively 

 dilated and contracted, giving the appearance of a vermicular 

 motion, and what is commonly called peristaltic. This motion 

 may be propagated either upwards or downwards, and the direc- 

 tion of it is in the one or the other way, as the motion happens 

 to begin at the upper or lower extremity. 



CCXXIV. The motion of the stomach is not so simple. Its 

 muscular fibres are in like manner irritable by dilatation, and 

 its circular fibres must therefore be in some measure subjected 

 to a successive dilatation and contraction. But though the di- 

 rection of such motions is from the left to the right, this does not 



