GROWTH OF A TRANSPLANTABLE TUMOR IN MICE Si 
puncture, while in other cases lacking these almost entirely, 
makes the actual size a very variable matter and not too accu- 
rate a measure of true growth. Undoubtedly, histological prepa- 
rations showing the number and extent of mitotic figures in a 
microscopic field of a given area would be one of the best methods 
of recording actual growth. This, however, is not practical. 
Sample records of mice showing various reactions toward the 
tumor implants are given below. 
It does not seem necessary to reproduce the records in detail 
for all the mice observed, though these have been preserved and 
will be presented in a later publication. 
Mice were inoculated in ten age groups: two, four, six, eight, 
ten, twelve, fourteen, sixteen, eighteen, and twenty or over 
Sample of Records. 
Actual Mice— Selectes Cases ~(N)Series. 
NO.OF MOUSE AGE SEX 2 Weeks 3 Weeks 4+Weeks 5S Weeks 6 Weeks 
Jaz 12 YS  TinyMss @ Small Mass @ Swilias @ Mas @ Negative 
160 6 i eFenkess Small Mass ® Negative Negative Negative 
513 4 FS Small Mass @ — Fishead Negative Deas »———+# 
S17 4 AS. , Negelwe Negative Negative Negative Negative 
days, respectively. In calculating the amount of growth ob- 
served, a single observation is the unit employed. Thus in the 
sample records given above, mouse 132 has six observations, 
four of which show some growth of the implanted tumor. In 
this particular mouse the percentage of growth is 80.0. 
On the other hand, mouse 513, which died between the fourth 
and fifth week after inoculation, has only three observations and 
therefore contributes only this number to the total number 
recorded. By employing this method, it is possible to calcu- 
late the percentage of observations of all mice in one age class 
or at any one observation period, which show growth of the tumor. 
It further provides a standard by which both the common stocks 
and the back-cross generation can be compared. 
