THE DUODENUM. 567 



from one fourth to a line in length, and estimated by 

 Meckel to be about four thousand to the square inch. 

 These villi present, under the microscope, FIG. 182. 

 a foliated or fungiform appearance, covered 

 by epithelium, and containing a minute 

 plexus of blood-vessels, and a lacteal tube, 

 all united by cellular tissue. 



The lacteal forms the prominent part of | 

 each villus. It commences, in the apex of 

 the latter, by delicate branches, converging I 

 to a single trunk, which proceeds to the base of the villus, 

 and there unites with similar tubes from other villi. 

 It is not yet fully settled whether the lacteals begin by 

 open orifices, or by anastomosing loops. The latter opin- 

 ion is most strongly urged, though observations are not 

 wanting to prove the existence of both arrangements. 

 Those who deny that there are any open mouths, explain 

 the absorption of the chyle, on the principle of endosmosis. 



At the extremity of each villus, a mass of minute cells is 

 described by Mr. Goodsir, as surrounding the loops of the 

 lacteals. He regards them as true agents of absorption, 

 first receiving the chyle, and, on becoming distended, 

 transferring their contents, by solution or deliquescence, to 

 the lacteals. It has been observed that, during digestion, 

 these cells become erect and turgid with chyle, while in 

 the interval they are found relaxed and empty, and pre- 

 sent the appearance of a collection of granular germs. 

 These cells are short-lived, being constantly destroyed, and 

 as constantly renewed. 



Tbe mucous coat of the duodenum, besides the simple 

 follicles of Lieberkuhn, scattered every where throughout 

 the mucous tissue, contains also the glands of Brwiner, 

 (Fig. 183.) 



These glands, situated in the sub-mucous tissue, sur- 

 round this intestine in the form of a layer of white bodies 

 of the size of hemp-seed, and of oval form. Each is said 

 to contain several hundred follicles whose excretory ducts, 



FIG. 182 represents a Villus and the commencement of a Lacteal. 



