Pathogenesis. 415 



ment of loops of intestines into a cleft during energetic move- 

 ments of the body, or pedicnlated formations or bands wliicli are 

 free at one end may in rolling become twisted around loops of 

 intestines. Under similar conditions strangulation is produced 

 by the spleno-nephritic ligament, a variety of strangulation 

 which is not rare. (In live cases observed by the authors the 

 left portion of the colon was always strangulated.) 



The jejunum, which is most motile and most slender, is 

 strangulated most frequently; other portions of the intestines 

 are less commonly aiTected in this manner. 



Pathogenesis. If the opening into which a portion of in- 

 testines has become displaced is narrow compared with the 

 caliber of this part of the bowel, or if a liand-like body has been 

 twisted around the intestines, the intestinal wall and its mesen- 

 tery are compressed to a certain degree and the lumen becomes 

 closed. In other cases the pressure becomes effective only if 

 the other additional factors mentioned above have caused fur- 

 ther portions of intestines and mesentery to become displaced, 

 or after the portion of the intestine that was first displaced has 

 become bloated in consequence of kinking or has become swollen 

 in consequence of venous (passive) congestion. 



The outflow of venous blood from the affected intestine and 

 its mesentery is interfered with in proportion to the pressure 

 exerted, while the thick-walled arteries with their high internal 

 pressure keep on pumping blood into the tissues, possibly in a 

 somewhat decreased amount. Hence, stagnation of blood 

 (stasis) soon occurs in the incarcerated portion of intestines 

 and also, owing to an increase in venous pressure, a diminution 

 of the velocity of the entire blood current with all the conse- 

 quences which have been discussed in detail under the head of 

 thrombosis of the mesenteric arteries (see page 396). At the 

 place of strangulation the compression produces an anemic ring. 



The rapidly increasing stasis, and the overloading with car- 

 bon-dioxide due to it, excite strong, frequent and occasionally 

 convulsive contractions in the strangulated portion of intes- 

 tines, causing colicky pains. The frequency and the intensity 

 of these convulsive contractions may be the greater, the longer 

 is the portion of intestine which is strangulated. A stronger 

 pressure, which, however, does not completely shut off the arte- 

 rial blood supply, clearly causes a considerable overloading of 

 the blood of the affected portion with carbon-dioxide, and causes 

 stronger contractions. Everything else being equal, strangula- 

 tion of the small intestines which are rich in nerves causes 

 more intense abdominal pain than strangulation of other por- 

 tions. 



Strong contractions may cause the entrance of more loops 

 through the place of strangulation by suction or traction if the 

 part situated towards the anus becomes distended, so that it 

 pulls on the part situated more towards the stomach (Wilms). 



