WALLACE O, FENN 475 



stant throughout the experiment. Fig. 3 is an exception, however, 

 since K decreases for the 3.2/1 particles and the-higher concentrations 

 of the 4.7m particles in about the same proportion. There is, there- 



fore, no increase in the value of -^^- In the two experiments which 



were not calculated. Experiment 4 showed an increase in this ratio 

 while Experiment 5 showed none. 



There are two causes for the variations in the experimental result: 

 (1) The suspensions used were not identical, for the material for each 

 experiment was separately prepared from the stock suspensions by 

 removing the large particles by centrifugalization. (2) There was a 

 slight tendency to aggregation on the part of the carbon which was 

 more marked in some cases than in others. 



In Fig. 3, three different concentrations of the 3.2/^ particles were 

 used, in the proportions 4 : 3 : 2, all of which have practically the 

 same K throughout. In Fig. 4, similarly, four different concentra- 

 tions of the 4.7/i particles were compared, all of which give approxi- 

 mately the same K. This is a better proof that the reaction follows 

 the law for a monomolecular reaction than the constancy of iv in a 

 single experiment because of gradual aggregation of the cells. 



While the agreement between theoretical and experimental ratios 

 in these experiments is admittedly rough, it seems surprisingly good 

 considering the difficulties involved. It is at least accurate enough 

 to discourage any attempts to measure the greater difi&culty of ingest- 

 ing a large particle compared to a small one by this method, which 

 was the original object of these experiments, because the limiting 

 factor is the availability of the particles, not the phagocytic capa- 

 bilities of the leucocytes. 



It should perhaps be emphasized here that a certain proportion of 

 the particles counted as phagocytized are merely stuck on the outside 

 of clumps of cells where it is impossible to distinguish them from 

 those inside. This does not occur with dead cells, however, and is 

 rightly regarded as the first stage in phagocytosis. 



Phagocytosis of Bacteria. 



It is interesting to inquire at this point whether the phagocytosis of 

 bacteria also follows the law for a monomolecular reaction, as does 



