476 DIGESTION. 



altered at will. This is effected by means of a key which fits 

 on two projecting points in the inner tube, and turns it round, 

 while the outer one is held fast by the fingers. The advantage 

 of this form over a simple tube with a shield at each end, is 

 that the cicatrix of the wound often thickens in healing, and 

 if the tube is not proportionately lengthened the outer plate 

 presses on the skin and causes ulceration. The disadvantage 

 of Bernard's canula is, that it is too small to allow the in- 

 terior of the stomach to be conveniently observed, and also, I 

 think, that the edge of the wound comes into contact with the 

 screw of the inner tube, and not with a smooth surface. 



These advantages may be readily obviated by increasing the 

 diameter of the tube and the width of the flange, and adapting 

 a key to the projecting points by which the outer tube may be 

 placed in the stomach and turned round as necessary. Such a 

 canula is represented in fig. 311. 



104. Operation for Gastric Fistula. Give the dog a 

 hearty meal, so as to distend its stomach completely and make 

 it lie close against the intestinal walls. 1 Anaesthetize the 

 animal by chloroform, taking care that the vapor is mixed 

 with a sufficient proportion of air. Lay it on its back on the 

 table, shave off the hair from the epigastric and hypochondriac 

 regions, and remove the hairs carefully by a sponge, so as to 

 prevent the risk of their getting into the peritoneal cavity. 

 Make a vertical incision about an inch and a half to one side 

 of the linea alba, preferably the left, and parallel to it, extend- 

 ing downwards from the lower edge of the costal cartilages to 

 a distance somewhat less than the diameter of the flange of the 

 canula. Divide the muscles parallel to the course of their 

 fibres. Tie every bleeding point before opening the perito- 

 neum, so that no blood shall get into its cavity. Open the 

 peritoneum on a director. Lay hold of the stomach with a 

 pair of artery forceps at a point where there are not many ves- 

 sels, and draw it forwards. Pass two threads with a curved 

 needle into the gastric walls at a distance from each other 

 about equal to the diameter of the tube of the canula, and 

 bring them out again at a similar distance from the points 

 where they were introduced. Make an incision into the gastric 

 walls, between the two threads, rather shorter than the diame- 

 ter of the tube of the canula. Put a pair of forceps, with the 

 blades together, into the incision, and then dilate it by sepa- 

 rating the blades till it is large enough to allow the canula to 

 be introduced. Push the canula into the stomach up to its 

 outer plate. Tie the stomach to it by the threads, and then 



1 Holmgren recommends the inflation of the stomach with air, by 

 nc:ms ,.l a tube passed down the oesophagus, as preferable to distend- 

 ing it with food. 



