The experimental study of cancer in a real sense began about 1900 with the discoveries of Jensen and Loeb concerning the relatively easy transplantability of certain spontaneous tumors of mice and rats from one animal to another. This, like most other discoveries, had long been anticipated, though Jensen's thorough investigations still stand today as a model of scientific achievement.
METHODS AND CONDITIONS OF TRANSPLANTATION
The methods and conditions that underlie such transplantation are still too little known, even to pathologists. The preferable technic was found years ago to be the grafting into the subcutaneous tissue of the axilla of the animal of a very small tumor fragment weighing only a few milligrams, by means of a trocar and cannula. The syringe injection of a mush of tumor cells is often followed by growths, but is not so satisfactory as the trocar method. Once the tumor particle is deposited in the