458 



DISSECTION OF THE ABDOMEN. 



narrow orifice, from three to four inches from the pylorus, and is situate 

 in a small prominence of the mucous membrane, at the inner and posterior 

 part of the duodenum (p. 445). A probe passed into the bile duct will 

 show the oblique course (half an inch) under *he mucous coat. Some- 

 times the pancreatic duct opens by a distinct orifice. 



Microscopic structure of the mucous membrane. With the use of the 

 microscope, and with pieces of fresh intestine, the student will be able to 

 make out the nature of the villi, the glandular bodies, and the epithelium. 



Villi. When a piece of the lower part of the duodenum, from which 

 the mucus is washed away, is examined in water, the mucous membrane 

 will be seen to be studded over thickly with small projections, like those 

 on velvet. These bodies exist along the whole of the small intestine, and 

 are irregular in form (fig. 153, A ) some being triangular, others conical or 

 cylindrical with a large end. Their length is from ? V tn * 5W* Q ^ an 

 inch ; and they are best marked where the valvulse conniventes are largest. 

 In the duodenum their number is estimated at 50 to 90 in a square line, 

 but in the lower end of the ileum at only 40 to 70 on the same surface 

 (Krause). 



Each villus is an extension of the mucous coat, and is covered by col- 

 epithelium. One or sometimes two arterial twigs form a capillary 



twork beneath the mucous covering (fig. 144, A ), and end generally in 



single emerging vein. A single lacteal, or two forming a loop with 

 branches (fig. 151, B ), occupies the centre, and communicates with 



tr __ 



S 8 



a- ... - 

 w -^ 

 n: 



A. VESSELS OF THE VILLI IN THE MOUSE, IN- B. LACTEALS AND PLEXUS OF VESSELS IN TWO 



JECTED BY GERLACH (Kollicker). VILLI, INJECTED BY TKICHMAN. 



a. Artery, and 6, vein. a. Lacteal vessel, single in one villus, double 



in the other. 

 6. Plexus of vessels 



c. Plexus of lacteals below the villi. (Quain's 

 Anatomy.) 



plexus below the villus. Around the lacteals a thin layer of unstriated 

 muscular fibre is arranged longitudinally (Briicke). Nerves have not 

 been detected in the villus. 



Glands. In the glandular apparatus of the small intestine are included 



