Blood Fluids in Intracellular Digestion. 337 



puscles and 2 volumes of serum (S. K. D.'s), which had been heated to 60° C. 

 for 18 minutes. 



Tube III. — One volume of 10-per-cent. suspension of ox red blood cor- 

 puscles and 2 volumes of normal salt solution. 



These tubes were then incubated at 37° C. for one hour, after which, by 

 repeated centrifuging and washing in normal saline solutiou, all traces of 

 serum were removed. The red blood corpuscles thus obtained were then 

 suspended in a volume of salt solution equal to the original volume of the 

 suspension of ox red blood corpuscles, and an equal volume of a 1 in 10 

 trypsin solution was added. The tubes were again placed in the incubator 

 at 37° C. for three hours, and after that period were put in the ice chest, 

 remaining there overnight. 



On examination the next morning, Tube I, that is the tube in which the 

 ox red blood corpuscles had been acted on by the unheated serum, showed 

 marked digestive changes, evidenced by hemolysis and change of colour of 

 the liberated haemoglobin, whereas in the case of Tubes II and III, in which 

 the ox red blood corpuscles had been brought in contact with heated serum 

 or with normal saline solution before the addition of the trypsin, no digestion 

 had taken place. 



The conclusion that is drawn from this experiment, which was repeated on 

 several occasions with identical results, is that the unheated serum acts in 

 some way on the red blood corpuscles, so as to render them susceptible to 

 digestion by trypsin. 



Further experiments, with exactly similar results, were made, in which a 

 leucoprotease solution was substituted for the trypsin solution. It was also 

 found that normal rabbit's serum, although without any hsemolytic action on 

 human red blood corpuscles, had the power of, in some way, acting on these 

 cells, rendering them susceptible to digestion by solutions of trypsin. 



However, human red blood corpuscles, which had been brought in contact 

 with rabbit's serum which had been heated to 60° C. for a few minutes, 

 were quite unaffected by such trypsin solutions. 



Substituting bacteria for red blood corpuscles, a series of experiments 

 showed that, in the case of a strain of B. Friedldnder and some other coliform 

 organisms, a very distinct digestion, evidenced by the loss of opacity of the 

 emulsion, was brought about when such organisms had been previously acted 

 on by unheated serum and afterwards treated with solutions of trypsin or 

 leucoprotease, whereas when the organisms had been treated with serum 

 heated to 60° C, or simply suspended in normal salt solution, both trypsin 

 and leucoprotease solutions were quite inert. 



These experiments show conclusively that the blood fluids modify the 



