SUB-CUTANEOUS INOCULATION 171 



In a large number of cases it is only necessary after cutting the hair, to rub 

 the skin with a [2 per cent, solution of lysol or a] O'l per cent, solution of oxy- 

 cyanide to render it aseptic. But for more perfect asepsis the skin should 

 be scrubbed with soap and a nail brush, washed with an antiseptic solution, 

 rinsed with alcohol and wiped with sterile filter paper. 



(i) Intra-dermal inoculation. 



1. Shave and cleanse the part but use no antiseptics. 



2. Scarify the skin very superficially with a bistoury, or pick up the skin 

 in the fingers and shave off the epidermis with the blade of a sharp knife. 



3. Bub the material to be inoculated into the prepared part with a sterile 

 glass rod or a piece of sterile wool held in a pair of forceps. 



In some cases, it is sufficient merely to rub the skin briskly with a sponge soaked 

 in the material without scarifying or scraping the surface. 



As a rule, the material should be inoculated into some part of the skin of 

 the body which the animal cannot reach, such as the dorsal surface of the 

 ear, the skin of the back, or the root of the tail. This rule applies to the 

 inoculation of all species of laboratory animals. For some viruses there are 

 special sites used for inoculation, the eyelids or eyebrows in syphilis, for 

 example. 



(ii) Inoculation on the surface of mucous membranes. 



Abrade the surface of the mucous membrane, as in the preceding case, by 

 scraping it with the blade of a knife, and spread the virus over the surface 

 thus abraded. Sometimes it is better, before inoculating the mucous mem- 

 brane, to cauterize it with a moderately hot iron or platinum rod so as to 

 produce a superficial slough. 



(iii) Sub-cutaneous inoculation. 



A. Of a liquid. 1. Shave and cleanse the skin. 



2. Pick up a fold of skin between the thumb and index finger of the 

 left hand, insert the needle at the base of the fold, inject the fluid and with- 

 draw the needle. Care must be taken to see that the fluid does not find its 

 way out again through the needle puncture and that the injection is not 

 made into the muscles. [By lightly pressing the fold in which the puncture 

 has been made between the finger and thumb and twisting it gently, exuda- 

 tion through the puncture can almost always be prevented.] 



B. Of a solid. 1. Shave and cleanse the part. 



2. Make a small incision through the skin with a bistoury, separate the 

 sub-cutaneous tissue with a director over a sufficient area and then introduce 

 the material to be inoculated into the pocket with a pair of sterile forceps. 



3. Put a stitch or two into the incision and cover it with a little collodion. 

 Note. As has already been stated above, inoculations are most satisfactorily 



made into some part of the body that the animal cannot reach ; they are however 

 often made beneath the skin of the abdomen or thigh. 



When the material to be inoculated is solid, some part of the body where the skin 

 is very loose should be chosen, as for instance, the flanks or the groin. 



(iv) Inoculation into lymphatic spaces. 



In the frog, inoculations are frequently made into the sub-cutaneous 

 connective tissue which consists of large inter-communicating lymphatic 

 sacs. 



A. Dorsal sac. The dorsal sac is situated over the posterior part of the 

 back. The animal's hind limbs are wrapped in a cloth so that it cannot 

 move, and by compressing the sides of the back with the fingers the sac is 



