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In order to discover these minuter differences it was necessary to 
subtilize the method. For this purpose the foliowing considerations 
were held in view. In the experiments mentioned above only the 
maximum and minimum capacity of resistance of the young erythro- 
cytes had been determined. . 
The determination of this capacity is, as is generally known, 
based on the following facts. 
When red blood-corpuscles are suspended in a salt-solution with 
an osmotic pressure less than 0,9°/, NaCl, they absorb water which 
causes them to swell. The lower the osmotic pressure of the salt- 
solution, the more water they will absorb. At last they burst and 
the haemoglobin, contained in them, enters the solution. The lower 
the osmotic pressure of the medium in which they can only just 
maintain themselves, the greater the capacity of resistance of the 
red blood-corpuscles. Seeing that not all the blood-corpuscles have 
the same capacity of resistance the minimum capacity of resistance 
of the blood is expressed by the most concentrated Na Cl-solution 
which already causes haemolysis. In this solution the weakest blood- 
corpuscles lose their haemoglobin. The maximum capacity of resistance 
of the blood is determined by the NaCl-solution in which the hae- 
molysis is complete, aud which cannot be resisted even by the 
strongest blood-corpuscles. Only these two salt-solutions have been 
determined in the above-mentioned investigations: as to the degree of 
haemolysis caused by the intermediate solutions every detail is wanting. 
By determining this degree we succeeded in discovering some 
qualities by which blood-corpuscles, newly formed after blood has been 
lost, are distinguished from the other, remaining ones. It was also 
found possible to study the mechanism of the regeneration more 
closely. The experimental method may be described as follows. 
2. Experimental method. 
The blood experimented upon was always that of rabbits. It was 
obtained by a slight cut in the ear and defibrinated by being beaten 
with 2 glass rods. A series of centrifugating tubes was filled with 
5 em? NaCl-solution in progressive concentrations, the difference 
between two successive concentrations being 0.02 °/,. To these 5 cm* 
0.1 em? of blood was added and the mixture was shaken thoroughly. 
Then the solutions Were left exposed to the temperature of the room 
for a few hours; subsequently they were centrifugated. In the tube 
where red blood-corpuscles no longer settle at the bottom, the haemo- 
lysis is complete. In the other tubes, where blood-corpuscles have 
; 19* 
