DKJKSTIOV 



Nfl 



Lieberkiihn ami the glands of Itrunm-r, there are 

 two very important glandular htnn-tun-. tin- lh-r 

 and the pancreas, which pour tlu-ir digestive juice* 

 into tin- small int. Mine ( lig. 5). The bile, which 

 is the secretion of the liver, in formal continually 

 by that orpin, lint tin- amount thus loin. 

 greatly influenced by the kirn I and quant it \ ot 

 food taken. It passes out of tin* liver by tin- two 

 hepatic duets, and much of it |>ae* by the 

 duct into the gall-bladder, where it is stored up. 



Fig. 6. Section of Intestinal Mucous Membrane : 

 L, lacteal in centre of villiix; E, epithelium covering villas; 

 B, blood-vessels represented; F, follicle of Lieberkiihn; 8, 

 part of a solitary gland ; M, muscular fibres. 



From this the bile passes into the common bile 

 duct, which joins the duct of the pancreas, and the 

 two open into the duodenum by a common aper- 

 ture. The bile is to be looked upon not only as a 

 digestive juice, but as a drain or channel of excre- 

 tion, whereby effete and useless matters are re- 

 moved from the body. The flow of bile is easily 

 restrained, as by inflammation of the duct, or the 

 presence of a tumour pressing on the duct, or a 

 gall-stone. In this case, the bile already formed is 

 reabsorbed with the blood, through the lymphat !<*, 

 and we have jaundiee due to absorption of tin- 

 colouring matter of the bile. The secretion of bile 

 goes on before birth ; the nieconimn of infants con- 

 sisting chiefly of biliary matter. The pancreas is 

 very similar in structure to a salivary gland. It 

 secretes the pancreatic juice which pours with the 

 bile into the digestive system. The mucous mem- 

 brane of the small intestine contains, in addition t<> 

 the structures already mentioned, little projec- 

 tions called villi (fig. 6). These are not, to any 

 great extent at least, secretive, l.nt they are im- 

 portant absorbante. This property they -lum- 

 with the whole of the digestive -\-t-m, through 

 any part of which, ami esp- ( -ially through the walls 

 of the stomach and small intestine, digested matter 

 passes into the numerous Mood-capillaries which 

 form everywhere a dense network. The villi are 

 peculiar, however, for each one contains, in addi- 

 tion to blood-vessels, a small lymph vessel or 

 lacteal. Nearly all the fat absorbed by the diges- 

 tive sy-tem is taken up l>y the little e.-IU of the 

 villi, and passes on into the lacteals, and thence 

 to the blood (fig. 7). If some osmic acid, which 

 blackens fat, be poured into the intestine of a milk 

 rabbit, killed during active digestion, and if the 

 villi be examined with a microscope, they will 

 be seen to have been blackened, especially at their 



U|M, while the rmt of the intentine will 



nerved itM ordimuy colour On further 

 tion it will IN- 



tlllll tin- I'llt ha* 

 Ulk'-n Up ill In 



lobules by 



tip- '.II- <., \.-iiii;; 





Fig. 7. The Top of a Villa* : 

 Ft globule* are repmratrd a* BM*> 



iiu- tlirnuith one of UM epithelial 



cell*, F. on through the UMM at 



tli.- villa*, I. into UM 



lacteal. L. 



tip- villi, and that 

 they are pAtwing, in 

 a way which in ax 

 yet not definitely 

 settled, into the 

 central lacteal. 



The small inteit- 

 tine is a tul- of 

 great iimxirtance, 

 and in order to in- 

 crease it total area, 

 the mucous mem- 

 brane is elevated, 

 in the upper part, 

 into transverse folds 

 (the valvuhi* conniventes, fig. 8). 



The unabsorbed food, mixed with the various 

 secretions we have mentioned, now parses into the 

 large intestine, when loth digestion and absorption 

 go on, although to a less extent. The large intes- 

 tine is only 5 feet in length, but it* girth i- much 

 greater than that of the small intestine. It com- 

 mences with the cjecum. a dilated part, into which 

 passes a little blind canal ( the vermiform appen- 

 dix ), a large and important structure in some 

 animals. Tne food remnant (f-cal matter) w pre- 

 vented, under ordinary circumstances, from passing 

 back into the small intestine, by a double fold of 

 mucous membrane (the ilio-ca-cal valve, fig. 9). 

 The large intestine ascends on the right side ( ascend- 

 ing colon), crosses over to the left side (transverse 

 colon), and descends again (descending colon ). and 

 makes a bend (sigmoid flexure), and finally ter- 

 minates in a somewhat enlarged |>ortion ( rectum ). 



Fig. O.-OMUB inflated, drfed. 



and opt-m-d to ahow UM amafs- 



ment of the ralw : 

 . termlnaUnar UM UMUB ; 



Ing coioa ; c, *" l *^S*J- 



:;; 



MMmttMf t Mail tnm IBM lar 

 IntMUno : 9. the rrrmUona pp 

 dntoftheoMUi 



Fig. 8. Small In- 

 teaiine distended 

 and hardened by 

 alcohol, and laid 

 open to show 

 the valvube con- 

 nivuntei. 



The anal aperture i* clol by nuiM-le*. an internal 



sphincter of mm -triped. and an external of si rit-l 



tiVn-. The mueoiiH memlmme of the Inrgf int. 



ditVer- from that of the small ; 



iiig no villi. or Bninner glands, Lielwrk 



solitAn- glamls are present, but the aggregmtioa ol 



the Utter into Peyer's patches is nowhere to be 



found. 



