LESSON 63.] NUTBrnON IN MAN. 215 



certain vessels, whose function it is to absorb the nutriment and con- 

 vey it into the circulation, to supply the blood positively lost by the 

 various glandular bodies, all of which have secreted or formed some- 

 thing from it ; these are the lacteals, already referred to. 



LESSON LXIII. 



NUTRITION IN MAN, CONTINUED. 



938. The precise relation of the lacteals to the villi of man, has 

 not yet been determined, owing to the difficulty of meeting with villi 

 distended with chyle ; but in the lower animals we can feed, and sub- 

 sequently kill, at any required moment, a Dog, or Cat, &c., and at 

 once proceed to make the necessary examination. 



939. These vessels appear to be much larger than capillary blood- 

 vessels, and one only is found in a villus which traverses its cen- 

 tral axis, and terminates in a coecal, or enlarged end. 



940. But how does the chyle get into the lacteals ? This is a 

 very difficult question to answer, and one to which no satisfactory re- 

 ply has yet been given. Many theories have been advanced, but no 

 authenticated observations have as yet been published. 



941. Some investigations made on this subject,* but not yet 

 given to the world, lead to the conclusion that the apices of the 

 viili open, and that the chyle is received directly in at the enlarged 

 termination of the lacteals ; it must be conceded, however, that this 

 fact is very difficult of verification, for the tissue, when first seen, is 

 covered with a deep layer of mucus : the epithelium at the summit 

 of the villi, is, like the organs themselves, porrect (standing up), 

 and worse, it so soon dies. The only favorable circumstance in con- 

 nection with a transient glance is, the uprightness of the villi, so 

 that the spectator looks down upon and readily perceives their open 



* Thirty years ago, during the Author's studentship, desirous of obtaining information 

 on this subject, he killed a Cat, and proceeded to examine the small intestine as rapidly as 

 possible, whilst yet vitality remained in the tissue. He saw the summits of the villi attop&n, 

 apparently as wide as their own diameter, but they soon closed up, and remained shut. 



Subsequently he repeated this experiment to a party of distinguished medical men, in 

 London, including some of his teachers. 



Having to arrange the preparation under the microscope, he again saw the same sight, 

 but, owing to the rapid loss of vitality, the villi so soon closed that not more than two or three 

 of the gentlemen present had an opportunity of seeing any thing of this interesting exhibi- 

 tion, and then so hastily that it was far from satisfactory to them. He has not since repeated 

 this experiment. 



