174 EXPERIMENTAL INOCULATIONS 



B. Carotid. In all mammals, the carotid artery lies in close relation to- 

 the trachea in the middle of the neck, being contained in a sheath common 

 to it, the internal jugular, the pneumogastric and the great sympathetic. 



1. With the animal lying on its back and its head extended shave the skin 

 of the middle of the neck and wash it with an antiseptic. 



2. Make a longitudinal incision, a few centimetres long, in the middle line, 

 in front of the trachea. 



3. Divide the aponeurosis connecting the two sterno-mastoids on a director. 



4. Separate the cellular tissue along the trachea with the rounded end of 

 a probe and then, by pulling the sterno-mastoid outwards, the sheath of the 

 vessel will come into view. 



5. Open the sheath with a pair of forceps and a director. The artery will 

 be recognized from the vein by its larger size. Make the injection as described 

 above. 



(viii) Intra-peritoneal inoculation. 



A. Of a fluid. Every precaution should be taken not to perforate the gut. 



1. Fix the animal firmly on its back. [An assistant can hold it equally 

 well.] Shave and disinfect a few square centimetres of the skin of the 

 abdomen. 



2. Pick up the whole thickness of the abdominal wall between the thumb 

 and index finger of the left hand. 



3. Insert the needle of the syringe into the base of the fold in such a way 

 that the point is directed upwards, withdraw it a little, and then, altering 

 the direction of the point, pass it into the cavity of the abdomen. Inject 

 the material and withdraw the needle. 



The following method affords greater security. A curved 

 needle is used, in which the opening is situated in the 

 centre of the concavity of the arc (fig. 140). 



Insert the needle through the whole thickness of the 

 abdominal wall, including the peritoneum, and bring the 

 %n^o^noc e ulation tra " P oint to the surface ; the needle -opening is now within 

 the peritonea] cavity, and the material is injected. The 



point of the needle being outside all the time that the injection is being made no 

 injury can be done by it to the gut. 



B. Of a solid. 1. The animal is fixed on its back, and the skin of the 

 part shaved and cleansed. 



2. Make an incision in the median line, the length of the incision varying 

 with the size of the substance to be inoculated. 



3. Cut through the aponeurosis, using a director to avoid injuring the 

 intestine. 



4. Take hold of the aponeurosis on each side with pressure forceps, and 

 hold it up as much as possible to prevent the intestines protruding. Intro- 

 duce the material to be inoculated into the wound and push it well under the 

 muscular layer into the peritoneal cavity. 



5. Sew up the aponeurosis with silk, stitch the skin and cover the incision 

 with a layer of collodion. 



Note. The most careful asepsis is necessary in performing intra-peritoneal 

 inoculations. These inoculations should always be done with pure cultures or 

 with material which can be obtained free from contaminating organisms for, if 

 sputum, excreta, etc., are injected into the peritoneal cavity the animal will very 

 quickly die of peritonitis. [But see Chap. XVIII. Sect. IV.] 



C. Collodion sacs. In their researches on cholera toxin, Metchnikoff, Roux 

 and Salimbeni devised a method of growing organisms in small closed collodion 

 sacs in the peritoneal cavities of animals. 



