ABDOMEN AND PELVIS 



479 



Inferior mesenteric plexus (plexus mesentericus inferior). 



Dissect out carefully the filaments of the sympathetic nerves sur- 

 rounding the branches of the artery and trace them to the intes- 

 tinal wall. What relation do they bear to the aortic plexus (plexus 

 aorticus abdominalis) f Study the latter now also. 



FIG. 250. 



A. colica media 



A. mcsenterica 

 superior 



A. mesenterica 

 inferior 



A. colica sinistra 

 Ramus descendens 



A. haemorrhoidalis 

 superior 



The inferior mesenteric artery. The small intestine has been laid over to the right. The transverse 

 colon has been turned upward and the sigmoid flexure spread out. (After Gegenbaur, Lehrb. der Anat. 

 des Mensch., Leipzig, 1899, 7 AufL, Bd. ii. p. 279, Fig. 542.) 



(d) Left mesocolic lymphatics. 



Do you find any lymph-nodes? What is the course and destina- 

 tion of the lymphatics draining the colon descendens and colon 

 sigmoideuni ? 



Mesenterial Small Intestine (Intestinum tenue mesenteriale). 



That portion of the small intestine which in the adult is at- 

 tached to the posterior abdominal wall by a mesentery is known 

 as the intestinum tenue mesenteriale. (Vide Figs. 251-3 and 

 Spalteholz, Figs. 565, 566, 568, 569.) 



It is arbitrarily divided into an upper one-third (two-fifths, 



