Pathoo'enesis. 



397 



liody (/() ; tlie art. colira veiitralis also forms anastomoses "vvitli the art. col. lateralis. 

 If one adds that there are anastomoses between the art. colica dorsalis and the art. 

 colica media, and also between the latter and the cranial branch of the art. mesent. 

 post, (e) and between all branches of the latter (o), one can easily see that blood 

 can get abundantly into the territory of the branches of the art. mesent. ant., either 

 from the art. cceliaca or from the art. mesent. post, and into the art. mesent. post., 

 and also from neighboring vessels, even if either one of the arteries named is oblit- 

 erated and the pressure in it is decreased. It is also important and should be em- 

 jihasized that intestinal branches, whether they arise from main trunks or from 

 arterial arches, and the branches in the intestinal wall in the mesentery are con- 

 nected by rich anastomoses, as can be seen in Fig. 40. 



Fig. 40. The mesenteric arteries of the horse. (Adapted partially from Ellenberger 

 and Baum ; the vascular anastomoses are drawn after a Teichmann-Preparation.) 



Narrowing or closure of the lumen of the mesenteric arter- 

 ies produces a disturbance in the blood circulation of the intes- 

 tines onh^ if the arterial pressure in the affected portions of the 

 intestines becomes markedly lower and if consequently the cur- 

 rent in the capillaries becomes very much decreased. Marek's 

 animal experiments have shown that total and sudden closure 

 will not be followed by recognizable disturbances of circulation, 



