IOIS THE AMERICAN NATURALIST. (VoL XXXV. 
exhibited pathological conditions with development of fever, or 
very often died soon after the transfusion. The hemoglobin of 
the foreign erythrocytes appeared in the bladder immediately 
after the transfusion, and often more hemoglobin was given 
off than was contained in the injected blood. The dissolving 
of red blood corpuscles by the serum of foreign blood was first 
observed under the microscope by Creite. 
Landois found, in some cases, that the dissolving of the 
injected blood elements did not occur. In transfusions between 
the horse and ass, wolf and dog, rabbit and hare, no hemoglobin 
appeared in the urine; the animal, even after the injection of 
a large amount of blood, showed no pathological symptoms, but 
behaved precisely as after an injection of blood from one of its 
own kind. Landois concluded that only animals of very closely 
related species can exchange blood with impunity. The question 
then arises, How closely related must animals be in order that 
their blood may be “ physiologically identical ” ? 
The method of blood transfusions is not adapted to extensive 
comparative researches. But the *globulicidal" action of a . 
blood serum can be observed to advantage in a test-tube. To 
10 c.cm. of the serum of some mammal let there be added three 
drops of foreign blood from which the fibrin has been removed, 
and let the mixture be kept at 38? for fifteen minutes. The 
mixture is at first opaque, because of the added erythrocytes, 
but at the end of the fifteen minutes the fluid regains its trans- 
parency and acquires a bright red, owing to the dissolving of 
the coloring matter from the added red corpuscles. Buchner 
found that if the serum is heated to 55? its power of dissolving 
foreign corpuscles is quite lost. Buchner also found that serum 
would dissolve the white corpuscles of foreign blood. 3 
The loss of the dissolving power of serum as a result of 
raising the temperature shows that the dissolving power 
depends upon chemical and not upon physical factors, since, by 
heating, the osmotic tension of the serum is not changed. 
The blood of cold-blooded animals does not respond to the 
test so readily as the blood of mammals, the nucleated cor- 
puscles evidently possessing greater resistance. Non-defibri- 
nated mammalian blood requires longer for the dissolving of its 
