ANIMAL EXPERIMENTS. 489 



III. Animal Experiments. 

 (A) Infection. 



i. Subcutaneous Inoculation. — After the skin in some part has 

 been washed with 1 : 1000 corrosive sublimate solution, a shallow 

 incision is made with scissors, and inoculating material is introduced 

 beneath the skin by means of a stout platinum wire with a loop. 

 Mice are usually inoculated above the root of the tail, they being 

 simply held by the tip of the tail and allowed to hang into a glass 

 which is covered in great part by a piece of board. Guinea-pigs and 

 rabbits are inoculated on the side of the thorax. 



2. Subcutaneous injection is usually carried out with Koch's 

 rubber-ball injection syringe or with Strohschein's syringe. A fold 

 of skin is picked up upon some part of the body, and the needle intro- 

 duced in the direction of the fold. If several cubic centimeters are to 

 be injected, it may be simply done as follows : Upon a graduated pipet 

 is fastened a short piece of rubber tubing provided with an injection 

 needle, and the whole sterilized. The pipet is sucked full, and the 

 fluid forced out with the mouth or a rubber bulb. 



3. Intraperitoneal injection is made by perforating the ab- 

 dominal wall at a single thrust with a sterile hollow needle ; then, 

 cautiously advancing the needle, the fluid is injected. 



Eegarding infection by feeding, inhalation, etc. , consult more exten- 

 sive works on technic. 



(B) Observation. 



Mice may be kept in sterile glass vessels provided with cotton and 

 closed with wire gauze. Larger animals must be kept in sterilized 

 cages or stalls. 



(C) Autopsy and Disposition of the Body. 



Autopsies must be made at once after death ; at least, the animal 

 must be placed on ice after death. The animal is placed upon a board 

 on its back and nailed or tied by its four legs. The abdomen and chest 

 are thoroughly moistened with sublimate solution and then the abdom- 

 inal cavity first opened with a sterile knife. The abdominal walls are 

 separated, and from the spleen, liver, and kidneys, some blood (or tis- 

 sue juice) is obtained with a sterile platinum loop and smeared at 

 once upon previously prepared agar plates. The organs are carefully 

 cut out, avoiding contact with the intestines, and placed in absolute 

 alcohol for further examination. Then the thorax is opened with 

 scissors, and blood removed from the heart and also the lungs. These 

 organs are also placed in alcohol. Before each operation the instru- 

 ments must be carefully heated to a glow or thoroughly burned. It is 

 better to have numerous sterilized instruments ready. The hands 

 must be perfectly clean. 



In interpreting the findings at the autopsy it is to be remembered 

 that often very soon (sometimes during the death agony) micro-organ- 



