WEISMANN'S THEORY OF THE GEPMPLASM 75 



guinea-pig, and pieces of dog's skin to the guinea- 

 pig, and always found that they died, or were thrust 

 out as foreign bodies. 



Precisely the same results follow transfusion of 

 blood between animals of different species. There 

 is complete agreement among investigators. When 

 the blood is made to flow directly from the vessels 

 of one animal to the vessels of an animal of a 

 different species, as from the dog to rabbit, or from 

 dog to sheep (or vice versa) ; or when it has been 

 first freed from fibrin and then injected, the result 

 is always the same. ' We have always found,' says 

 Ponfick, summing up the results of the investiga- 

 tion, ' not only that blood of another species acts in 

 strong doses as a poison, and in weaker or smaller 

 doses is harmful, but that (and this seems to me my 

 most important result) in every case the blood- 

 corpuscles are destroyed almost completely, pro- 

 bably quite completely.' In a very few minutes, 

 in the case of disharmonic kinds of blood, the red 

 corpuscles degenerate, and the haemoglobin, be- 

 coming dissolved in the blood-plasma, soon appears 

 in the urine. In the case of transfusion of similar 

 blood between individuals of the same or of very 

 closely related species, the haemoglobin does not 

 appear in the urine except after very large doses ; 

 and Ponfick infers that the red blood-corpuscles, 

 either all of them or most of them, remain un- 

 changed in the new animal. 



Landois has carried out transfusion between the 

 remotest species, between different families of 

 mammals, and between mammals, birds, and 



