GASTKIC DIGESTION. 



343 



When it is certain that all the bleeding has stopped, the peritoneum is to be 

 opened upon a director. On stretching open the wound the distended stomach 

 comes into view, its oblique muscular structure being plainly visible through its 

 serous covering. The gastric wall should then be seized with a pair of artery- 

 forceps at a point where there are not many vessels and drawn forward. Two 

 strong silk threads are then passed into the walls of the stomach with a curved 

 needle, at distances from each other about equal to the diameter of the tube of 

 the cannula, and brought out again at a similar distance from the points where 

 they were introduced. An incision is then made into the gastric walls, between 

 the two threads, rather shorter than the diameter of the tube of the cannula. Im- 

 mediately some bubbles of gas escape and some of the fluid contents of the 

 stomach, which must be sponged off. The opening into the stomach is now to 

 be stretched with ;t pair of blunt hooks until it is large enough to pass the inner 

 flange of the cannula, which is to be then introduced 

 and pushed into the stomach up to its outer plate. 

 The form of the cannula usually employed is repre- 

 sented in Fig. 145 ; it consists of two tubes, each ter- 

 minating at one end in a circular plate, the two tubes 

 being cut with a screw-thread, on the outside of one 

 and the interior of the other, so that the distance be- 

 tween the two plates, when the tubes are joined 

 together, may be altered at will. After the insertion 

 of the cannula the stomach is fastened to it by the 

 threads which were previously inserted, and the ends 

 of these threads passed through the abdominal walls 

 in such a way as to fasten the stomach to them, and 

 at the same time when tied together keep the edges 

 of the wound in the abdominal walls in apposition. 

 The sutures need not be carried through the perito- 

 neum, and no additional means of closing the wound 

 is necessary. After the animal has recovered from 

 the anaesthetic, the cannula must be left uncorked for 

 at least half an hour after the operation, for the dog is 

 almost certain to vomit, and were the cannula not open 

 the contents of the stomach would be apt to be forced 

 past the side of the cannula into the abdominal cavity, 

 and cause the death of the animal. 



After the operation the animal must be fed on 

 milk for two or three clays and kep,t in a warm place. 

 When recovering from the anaesthetic the animal will 

 be very likely to make attempts to tear out the cannula 

 with his teeth, a result which would be apt to be fatal 

 to the dog. The only way this accident may be 

 guarded against is by careful watching. It will not 

 do to muzzle him and leave him, for if he then should 

 vomit he would choke to death. After the first day 

 the wound becomes so tender that no further attempts 

 at tearing out the cannula are usually made. On the 

 second or third day after the operation the margin of 

 the wound becomes much swollen, and it is then 



necessary to lengthen the tube of the cannula so as to avoid ulceration of the 

 skin from pressure of the external flange. By this time adhesions have been 

 established between the edges of the wound in the stomach and the abdominal 

 walls, and the wound in the latter having healed, with the exception of the space 

 occupied by the tube of the cannula, the cavity of the stomach communicates 

 with the exterior by means of a more or less elongated fistulous tract (Figs. 146 

 and 147). The cannula may be closed by a cork'or it may be fastened with a 

 valve. 



If everything goes well, the dog will be ready for experiments in about a 

 week. - 



In ruminant animals fistulous openings may be made injo anyone of the four 

 stomachs or gastric compartments, although, of course, an opening into the fourth 

 stomach is the only one through which gastric juice may be collected. The 



Fig. 145. — Cannula fob 

 gastkic fisttjl2e. 

 {Bernard.) 



A B, section of the cannula ; e, 

 flange of the cannula; C, projections 

 on the interior of tube which fit in 

 key, D, so as to lengthen or shorten 

 tube ; E, opening of tube. 



