Page:Defensive Ferments of the Animal Organism (3rd edition).djvu/200

 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 apparently 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 hæmolysis 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. Hæmolysis 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 hæmoglobin, 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 hæmolysis of the red corpuscles which, though present, have been overlooked.