LYMPHATIC VESSELS AND GLANDS. 277 



retarded ; and in paraplegia the intestines appear after a time 

 much weakened in their power, and costiveness, with a tym- 

 panitic condition, ensues. Immediately after death, irritation 

 of both the sympathetic and pneumogastric nerves, if not too 

 strong, induces genuine peristaltic movements of the intestines. 

 Violent irritation stops the movements. These stimuli act, no 

 doubt, not directly on the muscular tissue of the intestine, but 

 on the rich ganglionic structure shown by Meissner to exist in 

 the submucous tissue. This regulates and controls the move- 

 ments, and gives to them their peculiar slow, orderly, rhyth- 

 mic, and peristaltic character, both naturally, and when arti- 

 ficiallv excited. 



CHAPTER X. 



ABSORPTION. 



THE process of absorption has, for one of its objects, the in- 

 troduction into the blood of fresh materials from the food and 

 air, and of whatever comes into contact with the external or 

 internal surfaces of the body ; and, for another, the taking 

 away of parts of the body itself, when, having fulfilled their 

 office, or otherwise requiring removal, they need to be re- 

 newed. In both these offices, i. e., in both absorption from 

 without and absorption from within, the process manifests some 

 variety, and a very wide range of action ; and in both it is 

 probable that two sets of vessels are, or may be, concerned, 

 namely, the bloodvessels, and the lacteals or lymphatics, to 

 which the term absorbents has been especially applied. 



Structure and Office of the Lacteal and Lymphatic Vessels and 



Glands. 



Besides the system of arteries and veins, with their inter- 

 mediate vessels, the capillaries, there is another system of 

 canals in man and other vertebrata, called the lymphatic sys- 

 tem, which contains a fluid called lymph. Both these systems 

 of vessels are concerned in absorption. 



The principal vessels of the lymphatic system are, in struc- 

 ture and general appearance, like very small and thin-walled 

 veins, and like them are provided with valves. By one ex- 

 tremity they commence by fine microscopic branches, the lym- 

 phatic capillaries or lymph-capillaries, in the organs and tissues 



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