911. | Spontaneous Cancer in Mice. 537 
| | 
Nature of tumour transplanted, | | Into other Tied Llomaals. 
| Into mouse | eo cae Z 
and protocol number of the steel | spontaneously 
mouse bearing it. | . | affected mice. Young. Old. 
‘ChnnGig0V(s WP cana ean aaa eee 266 | + 0/2 0/349 
re 273 | i | 0/1 0/337 
56. ty aS Aa en 349 + | 1/7 5/180 
of (0) ep REC R ARE Be ene aAD 357 + | 0/4: 1/59 
Sebaceous carcinoma......... 292 | + 0/3 4/42 
Adeno-carcinoma. Mamma 282 © + | 2/4* 4/26 0/12 
é OY 329) | A | 2/7 8/52 
i sea | # 0/5 0/16 0/16 
- ph £338 He 0/5 2/60 0/15 
i ep ie soil x 0/1 0/35 
. ists i 0/1 3/35 
5 other adeno-carcinomata 5 - | 0/10 Not tested in normals 
Spindle cell sarcoma ......... 460 | Not transplanted ; 0/8  16/t30" 0/5 
mouse killed 
Obey eet, Ja 16/16 | 5/58 43/1321 0/58 
| | 
* 2/20 when all inoculations are reckoned. 
growth of other spontaneous tumours than do normal animals. The question 
of the suitability of the soil afforded by cancer-mice to the growth of tumours 
is a most important one. In order to study this question a little more closely, 
the behaviour of cancer-mice to different transplantable tumours has been 
investigated. Five experiments with 46 spontaneously affected mice have 
been undertaken with four different tumours representing different types of 
growth. 
In order to employ control animals as comparable as possible to the 
cancer-mice, cancerous mice from the breeding experiments of the laboratory 
have been used, and as controls, their sisters and other near relatives kept 
under exactly the same conditions and of the same age as the cancerous mice. 
The results of a typical experiment are seen from the chart (fig. 1), done 
with a rapidly growing carcinoma which usually grows progressively in a high 
percentage (Carcinoma 63). Expressed in figures, the result is, in young 
normals, six tumours in ten mice, 2¢. 6/10; in old normals, 5/10; in old 
non-cancerous females of the breeding experiments of exactly the same ages 
as the cancerous mice, 2/10 (plus three positive cases which died too early to 
settle definitely whether the tumour would have grown progressively) ; and in 
cancer-mice from the same breeding experiments, 4/7. 
On the whole, these experiments have failed to elicit any striking 
difference in suitability between spontaneously affected and normal animals. 
As in all transplantations of tumours, young animals show a greater 
susceptibility than older ones. In most of the experiments the transplanted 
