320 Cc. C. LITTLE 
eliminate it. The reaction of these mice is a clear case of what 
Loeb has recently considered under his study of the inheritance 
of the ‘individuality differential.’ This matter will be referred 
to later in more detail, but for the present it is interesting to 
note that the individuality differential of the tumor implants 
are the same, since they are all derived from what was the same 
piece of tissue. The study of the behavior of these implants has, 
therefore, a distinct advantage over Loeb’s method of implanting 
a piece of tissue from various individuals into other individuals 
and of studying the resulting reactions. In Loeb’s case it is 
obvious that there are two variables: 1) The individuality dif- 
ferential of the animal giving the implant, and, 2) the individu- 
ality differential of the host. Since these in turn are them- 
selves the composites of the activity of a dual structure, namely, 
the fertilized egg, it follows that the possibilities for confusion 
due to complexity of their organization are manifold. In this 
respect, the use of a biological constant such as the tumor 
J.W.B. has a great advantage. Coming as it does from a remark- 
ably homogeneous race of animals, it represents a tissue in 
which the individuality differentials contributed by its maternal 
and paternal ancestors are approximately, if not entirely equal. 
The result is a relatively great uniformity of response when- 
ever known genetic material of a relatively homogeneous nature 
is used as the host stock. 
Even within the Japanese waltzing race itself, the wonderfully 
uniform nature of the individuals is shown by the unfailing growth 
of the J.W.B. tumor in animals of this race. This can mean 
only that within this race types of implantation which would 
normally be as widely distinct as homiogenetic are to all in- 
tents and purposes autoplastic in their reaction. 
It follows, then, that when the tumor J.W.B. is used for im- 
plantation that much simpler conditions are realized than those 
that exist in Loeb’s material. Much of the indefiniteness which 
surrounds his hypothesis of syngenetic, homiogenetic, and 
heterogenetic transplantation and the resulting classes of toxins, 
vanishes, because the test of the individuality differential is 
reduced to the simple question of its treatment of a biologically 
constant implant. 
