3t) ORGANS 'OF DIGESTION. 



lous has also been applied to this coat. These villi are to be 

 found in abundance every where; but in the upper half of the 

 intestinurn tenue they are so numerous as to stud its whole sur- 

 face, and to be in contact with each other. They are from 

 one-fourth of, to a line in length; and some of them, when exa- 

 mined with a microscope, appear flattened and fungiform. 

 According to the estimate of Meckel,* where they are thickest, 

 every square inch of intestine^ furnishes about four thousand of 

 them, and by extending this computation, with a proper al- 

 lowance for diminished numbers below, their aggregate amount 

 is about one million/j- 



Each Villus is composed of an artery, a vein, and a lympha- 

 tic; all united by cellular substance. From the extreme vascu- 

 larity oT the mucous membrane, the blood vessels readily re- 

 ceive a fine injection and thereby become evident, forming a 

 very delicate vascular net-work in each of the villi. It is ascer- 

 tained that the lymphatic opens on its surface, but whether by 

 one or more orifices is yet unsettled. According to the cele- 

 brated Lieberkuhn, there is commonly but one orifice at the end 

 of each villus, and very rarely two: this assertion he considered 

 himself as having established by passing a current of air through 

 the villus till it was dried, and then slitting it open. Hewson, 

 Cruikshank, and W. Hunter, on the contrary, are said to have 

 found many more, amounting even to twenty, on such villi as 

 were gorged with chyle. The subject has been fruitful with, 

 controversy to anatomists, and ranks many distinguished cham- 

 pions on each side; but as from the minuteness of the parts un- 

 der discussion and the consequent necessity of microscopical 

 observations, it is exposed to much fallacy and illusion; and can- 

 not be satisfactorily settled, though the general analogies of 

 papillary structure are in favour of the latter authorities. The 

 more important fact, however, is conceded by the admission 

 of all, that there is a branc,h of the lymphatic system in every 

 villus; which has, for its function, the absorption of chyle from 

 the cavity of the intestine. 



* Manuel D'Anat. 



t This is probably much below their real number ; iu an observation at the 

 university we h?ive found the villi on the ilium at its lower part amounting 1 to 

 six thousand four hundred the square inch, as their shape, however, varies very 

 much* as we shall sec> a rule cannot be derived from this,. 



