Pathogenesis. 



441 



tracted elongated bowel may, at its anterior end, slip further 

 over the invaginated bowel. These factors may sometimes 

 bring it about that the invaginated intestines may be several 

 meters long. The increasing contractions of the invaginated 

 intestine with its mesentery causes continuous pain which, as 

 usually in displacements, becomes augmented by external or by 

 increased intraabdominal pressure. However, the pain is, as a 

 rule, not very intense. 



The lumen of the invaginated l)owel is considerably dimin- 

 ished from the start, and it may not rarely become entirely ob- 

 structed in consequence of swelling of the intussuscepted por- 

 tion, together with its mesentery. The larger the intussus- 

 cepted bowel, the less the lumen of the intussuscepting portion 

 will be diminished. Diminution or obstruction of the intestinal 

 lumen excites more ac- 

 tive, later on convulsive 

 contractions in the intes- 

 tines situated towards 

 the stomach; tliese con- 

 tractions are moderately 

 painful. The peristalsis 

 of the sections situated 

 towards the anus only 

 ceases when the invagi- 

 nated portion has lost 

 its contractility; this oc- 

 curs in consequence of 

 intense infiltration, ne- 

 crosis, secondary peri- 

 tonitis, or excessive com- 

 pression ; usually, how- 

 ever, only after a num- 

 ber of hours and even 

 days. As long as the in- 

 vaginated bowel moves, 

 the peristalsis pro- 

 gresses towards the 

 anus, even if complete 

 obliteration supervenes 

 eventually, because the 

 the peristalsis may not 



Invaj^ination in a horse. 



strangulation is not so severe that 

 progress from the invaginating to- 

 ward the invaginated portion. These contractions may be 

 sluggish; they continue for some time or even until the end, 

 and propel the serous, hemorrhagic fluid, that is extravasated 

 into the lumen, towards the rectum. 



The nutritive disturbances which are caused by the con- 

 gestion of the intestinal walls may be very variable in degree, 

 according to the nature of the affection, and lead to similar con- 

 sequences as they are found in internal strangulation; the im- 



