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decrease on the other, run so exactly parallel, that we are at once 
tempted to trace a connection between them. 
Moreover the weaker ones are found to decrease much more 
strongly than can be explained by mere loss of blood only. If no 
regeneration were to take place, the proportion between the weaker 
and the stronger blood-corpuscles would not be modified at all. At 
the regeneration, therefore, the number of weaker bloodeorpuseles 
must become relatively smaller since it is just the new bloodcorpuscles 
which have a great capacity of resistance. Even if the entire loss of 
blood had been made up for, this strong decrease of the weaker 
ones cannot be explained. The rabbit weighed 2000-grammes, con- 
tained, therefore, */,,, < 2000 = 160 gr. of blood. After 2 bleedings 
of 15 ccM. (that is about 20°/, of the whole) of the 80°/, erythro- 
eytes which are destroyed at 0.49°/, NaCl only 25°/, are found 
back. These weaker bloodeorpuseles decrease, therefore, much more 
strongly than can be explained by loss of blood only: they must be 
used in some way or other. Since, moreover, the increase of the 
stronger bloodeorpuseles runs parallel to the decrease of the weaker 
ones, we may with a great amount of probability assume that the 
young red bloodcorpuscles are built up out of the weaker ones. 
Now it can also be explained why the young blood corpuscles 
develop a greater capacity of resistance as more blood is withdrawn. 
The weaker bloodeorpuscles decreasing very strungly after every 
bleeding, the old bloodcorpuscles, which in the anaemic animal serve 
to build up the new ones, are already much stronger than the old 
bloodeorpuseles which are disintegrated in the normal animal for 
this purpose. As the material out of which they are built up grows 
stronger and stronger, the young blood-corpuscles are stronger too 
after each venesection. 
This also supplies us with one of the chief causes of the difference 
between erythrocytes, formed after bleeding, and those formed after 
poison-injections. 
Owing to the abnormally strong decrease of the number of blood- 
corpuscles after poison-injections, the newly formed cells could not 
but become very strong —- much stronger than after a few bleedings. 
5. Also in the blood the regeneration greatly surpasses the loss. 
Finally a conclusion may be arrived at as regards the degree of 
the regeneration. After 2 venesections about 20 °/, of the blood 
of the rabbit had been withdrawn. At the third bleeding 60 °/, 
bloodcorpuscles were found with a greater capacity of resistance 
