OBTAINING THE BLOOD-SERUM 175 



separated out one makes use of the centrifuge. In the 

 first case the serum is poured into a centrifuge tube, 

 and centrifuged for about five to ten minutes. It is 

 then easy to ascertain that the serum, which was ap- 

 parently free from solid elements, has now given off 

 a whole layer of red blood corpuscles during the 

 process of centrifuging a second time. Should this 

 remain in the serum, then during the dialysis 

 haemolysis would take place in the dialysing tube, 

 and the experiment would give faulty results. 



It happens, usually, that the experiment is so 

 arranged that, say, 1*5 c.c. of serum are taken from 

 .the centrifuge tube and employed as a control. 

 Only after this do we remove more for the test, 

 organ + serum. If at this point the directions 

 are not followed exactly, it may easily happen that 

 red corpuscles are found in the test, organ + serum. 

 Haemolysis appears during dialysis, and then we 

 have exactly the same conditions as arise when 

 organs are used which contain blood; only in 

 this case the contents of the corpuscles are 

 found, not in the tissue, but in the serum. It is 

 from non-observance of the rules given that we get 

 the observation that a serum, which is absolutely free 

 from haemoglobin, appears quite red at the end of 

 the experiment. It is the diffusion of water from the 

 outer fluid into the tube that has led to the haemolysis 

 of the red corpuscles which, though present, have 

 been overlooked. 



