342 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



1. Chemistry op the Gastric Juice. — That the gastric juice may be 

 obtained pure for analysis a fistulous opening has to be made into the 

 stomach, since the various other methods employed by Reaumur and 

 Spalanzaui, of allowing animals to swallow sponges and then withdrawing 

 them and obtaining the fluid by pressure, will not succeed in yielding 

 a pure gastric secretion, as it will evidently be contaminated with the 

 fluids of the mouth, pharynx, and oesophagus. 



The method of performance of gastric fistula originated in the 

 account of the celebrated case, reported by Dr. Beaumont, of the Cana- 

 dian trapper, Alexis St. Martin, in whom an accidental gunshot wound 

 of the abdominal walls left a fistulous tract communicating with the 

 cavity of the stomach. It was through the data obtained by Beaumont 

 from a study of this case that the first facts as regards the chemistry and 

 physiology of gastric digestion were obtained. Led by an account of 

 this case, the production of a similar fistulous opening communicating 

 with the gastric cavity on animals was first shown to be practicable by 

 Blondlot, and after him by Bernard. Blondlot's method was to make an 

 incision seven or eight centimeters long in the linea alba, commencing at 

 the xyphoid cartilage. The walls of the stomach were stitched to the 

 wound, and, after adhesion had taken place between the peritoneal cover- 

 ing of the stomach and the abdominal walls, an opening was made into 

 the cavity of the former, in which a tube was inserted. 



Bernard has, however, shown that it is not necessary to allow the 

 stomach to become adherent to the abdominal walls before opening it, 

 and the method which he recommended is one which is now generally 

 adopted. 



In making a gastric fistula, an animal must, of course, be selected in which the 

 stomach is large and lies close to the abdominal walls. The horse is, therefore, 

 inappropriate for such experiments, since in the horse the stomach is small, 

 deeply seated, and not in contact with the abdominal parietes. On the other 

 hand, rabbits cannot be employed, since their stomachs are never empty ; and 

 cats are very liable to die of peritonitis, to say nothing of the difficulty in their 

 subsequent management. In some birds with a muscular stomach, as, for example, 

 in the crow, gastric fistulas may be very satisfactorily made. The animal, how- 

 ever, which is, on all accounts, most suitable is the dog. Dogs are easily man- 

 aged, secrete pure gastric juice in abundant quantity, and are not very liable to 

 peritonitis. 



In order to perform the operation of making a gastric fistula on a dog. the 

 animal is well fed, so as to distend the stomach, or, after fasting twenty -fourhours, 

 the stomach may be distended by an injection of air through the oesophagus, and 

 is then chloroformed and securely fastened. The first step is to shave the hair 

 from the abdominal walls in the epigastric region, and to remove all the hairs 

 carefully with a sponge, so as to prevent their entering the abdominal cavity. An 

 incision is then made through the skin, commencing at the lower margin of the 

 costal cartilages and about an inch and a half to the left of the linea alba, and 

 extending downward parallel to this line for a distance a little less than the 

 diameter of the flange of the cannula which it is desired to use. Each muscular 

 layer is then to be divided in a direction parallel to its fibres, every bleeding point 

 being tied before the peritoneum is opened, so as to prevent the entrance of blood 

 into this cavity. 



