SEC. 7. THE LACTEALS AND THE LYMPHATIC 



SYSTEM. 



§ 235. We have seen that absorption does, or at least may, 

 take place from the stomach. We have also stated that a large 

 absorption, especially of water, occurs along the whole large 

 intestine. Nevertheless it is during the transit of food along 

 the small intestine that the largest and most important part of 

 the digested material passes away from the canal, partly into the 

 lacteals, partly into the portal vessels. The portal vessels are 

 simply parts of the general vascular system ; the lacteals, into 

 which we may at once say the greater part of the fat passes, are 

 similarly parts of the general lymphatic system, being in fact the 

 lymphatic vessels of the alimentary canal, and especially of the 

 small intestine. The only reason for the special name of lac- 

 teals is that, unlike the lymphatic vessels of other parts of the 

 body, the lymphatics of the intestine contain at times a fluid of 

 a milky white appearance. Hence for the better understand- 

 ing of absorption by the lacteals it will be desirable to study at 

 some length the whole subject of the lymphatic system. 



The lymphatic vessels may be said to begin in minute pas- 

 sages, possessing special characters, known as lymph-capillaries. 

 Broadly speaking these lymph-capillaries are found, in the mam- 

 mal, in all parts of the body in which connective tissue is found; 

 and they have special connections with those minute spaces in 

 connective tissue which we have already more than once spoken 

 of as lymph-spaces. These lymph-capillaries, which are fre- 

 quently arranged in plexuses, are continuous with other pas- 

 sages also minute but of a different and more regular structure, 

 the lymphatic vessels proper, which are gathered into larger 

 and larger vessels, all running like the blood vessels in a bed of 

 connective tissue, until at last all the lymphatic vessels of the 

 body join either the great thoracic duct which opens by a valvu- 

 lar orifice into the venous system at the junction of the left 

 jugular and subclavian veins, or the small lymphatic trunk 

 which similarly opens into the junction of the right jugular 

 and subclavian veins. The large 'serous cavities, peritoneal 

 and the like, are also connected with the lymphatics, and may be 

 regarded as part of the lymphatic system. 



398 



