90 Hypothesis of Structure of Germ Substance 
of different species. But this demonstration has not 
been afforded in a single instance of animal grafting. 
There are indeed examples of transfusion of blood 
which do not succeed when they are made from one 
animal to another of different species, whereas they do 
succeed perfectly between animals of the same species. 
There are the experiments of Bert upon the successful 
transplantation of a fragment of the tail of a mouse 
into the subcutaneous tissue at another part of the body 
of the same individual or of another individual of the 
game or a related species, as Mus decumanus and Mus 
rattus, whereas such a transplantation is not successful 
between species farther removed, such as Mus rattus 
and Mus silvaticus. There are the experiments of Ollier 
and Schmitt on the transplantation of fragments of 
bony tissue, which were successful in transplantations 
from one part to another of the same individual or to 
another individual of the same species, but failed be- 
tween individuals of different species. 
But all these experiments indicate only that there is 
more affinity between the parts of the same tissue or of 
similar tissues when they belong to individuals of the 
same species or of related species than when they are 
taken from individuals, of different species. They do 
not prove at all that there is more affinity between parts 
of different tissues, which come from the same individual 
or from individuals of the same species, than between 
parts of the same tissue taken rrom different species. 
On the other hand Joest’s experiments have demon- 
strated the possibility of true heteroplastic grafts in the 
annelids, in which it is easy to obtain transplantations 
“Oscar Hertwig: Die Zelle und die Gewebe. II, P. 2aff. 
