GROWTH OF A TRANSPLANTABLE TUMOR IN MICE 309 
TECHNIQUE 
a. Inoculation 
The technique of inoculation is that which has long been em- 
ployed by Tyzzer and is extremely simple. ‘The tumor, having 
been excised, is placed in a sterile Petri dish. A bit of it is then 
cut off with a clean pair of sharp curved scissors, placed on the 
lip of a trochar, and is pushed into the neck of the trochar by the 
blunt plunger. The mouse is then held firmly and the trochar 
pushed forward under its outer skin to the region of the right 
axilla where the bit of tumor is deposited; the trochar is then re- 
moved and sterilized and the process repeated for another mouse. 
No ether is necessary, for the mouse appears scarcely to feel the 
inoculation and no bleeding occurs. In mice younger than eight 
or ten days a slight modification of method is necessary. 
In these animals a small incision about 1 mm. long is made 
in a position approximately above the right kidney, care being 
taken to avoid cutting the peritoneum. A fine, blunt wire or 
the point of a pair of blunt forceps is then run forward under the 
outer skin to make a pathway for the tumor implant; the im- 
plant itself, cut as before from the tumor mass, is placed at the 
mouth of the incision and is pushed gently forward under the 
skin by the forceps or blunt wire. By lifting the skin in the 
region of the incision, it is found possible to draw in the im- 
plant by suction and in this way place it in a position where it 
is easier to push it forward to the region of the right axilla. 
In some cases the incision needs no further treatment, and in 
others where the skin has become slightly stretched or torn in 
the process, a single drop of flexible collodion applied after the 
implant is pushed forward, will serve to provide an air-tight and 
antiseptic method of closing the wound. 
It is also necessary to work rapidly with younger mice in 
order that they may not lose their body warmth and become 
inactive and repugnant to the adult mice when they are re- 
placed in the pen. It is further advisable to hold them for one- 
half or three-quarters of a minute wrapped in cotton bedding 
taken from their own nest, before they are replaced after in- 
