282 LABORATORY EXERCISES IN BACTERIOLOGY. 



with a fine hypodermic needle. The animal as a rule requires little holding. The 

 needle is introduced from the dorsal side of the ear. It is scarcely necessary to shave 

 the little hair from the skin, which is, however, to be well washed to begin with ; where 

 the hair is at all marked, however, it is best to shave the ear and wash it thoroughly. 

 One must usually compress the base of the ear in order to make the vein in its course 

 prominent ; a small rubber band about the root of the ear serves this purpose well. 

 The fluid in the syringe is carefully brought to the end of the needle so that no bubbles 

 of air will be carried in the process into the circulation. The needle is then introduced 

 into the vein as near the tip of the ear as practicable where the vein is straightest in 

 its course, care being taken that it really enters into the interior of the vessel. The 

 fluid is then forced gently and steadily into the vein, blanching its previous red line 

 as the blood is displaced. Before the needle is withdrawn the pressure at the base 

 of the ear should be released; and after withdrawal the tiny opening may be sealed 

 with collodion. A similar operation may be practised in case of the veins of a dog's 

 ear; in other animals and in deeper seated vessels it is necessary to expose the vein 

 by definite dissection. 



Intraperitoneal Inoculation. This may be performed with the hypodermic 

 syringe; or an opening may be made by regular surgical operation and through this 

 a solid material introduced into the cavity. 



The first procedure is relatively simple. The animal is fastened upon one of the 

 mechanical holders, the hair or fur removed from a small area of the abdominal surface 

 by means of the clippers and razor, and the surface well washed. The needle of the 

 syringe holding the inoculating material is inserted under the skin as in subcutaneous 

 injections, and then the abdominal wall is firmly pinched up into a comparatively 

 large fold, this practice removing the danger of puncturing the intestine. The needle 

 is next thrust well into the fold until its point is felt to be free in the cavity, when the 

 fluid is forced into the latter. The needle is now withdrawn and a drop of collodion 

 applied to the skin puncture (which is not in exact correspondence with the puncture 

 into the cavity, the latter being protected by the skin at a little distance from the 

 point of entrance into the cutaneous surface). 



In opening the abdomen for the introduction of solid infections the animal is 

 similarly prepared. The skin having been freed from hair and fur and the surface 

 cleansed, the site of operation is anesthetized by cocaine, after which an incision is 

 made through the skin with a sterile blade or scissors and the skin reflected from the 

 underlying tissues. The incision is to be made in the median line in order to minimize 

 the danger of bleeding. The tissue of the full thickness of the exposed abdominal 

 wall is now pinched up into a fold by the fingers and several sutures corresponding to 

 the size of the opening to be made are inserted through the entire thickness, passing 

 in and out of the peritoneum in their course ; these sutures are to be made transversely 

 to the line of incision in making the opening. This done, a small incision is cut with 

 a sterile instrument so as to open the cavity and through this the inoculation material 

 introduced. The opening through the wall is now closed by adjustment of the sutures; 

 after which the skin is drawn into place and closed by means of a second suturing 

 and the line of the skin wound sealed with a collodion dressing. 



Other Forms of Inoculation. Inoculations are sometimes made into the anterior 

 chamber of the eye, where the development of the consequent local lesion may be watched. 

 In this case the lids are held by proper retractors and the surface of the conjunctiva 

 irrigated with a solution of bichloride of mercury and afterward with sterile water; 

 after which, with a sterile cataract needle, the cornea along the junction with the 



