504 SCIENCE PROGRESS 



points to differences of method, and is in itself an indication 

 that the apparent increase of appetite is due to the artificial 

 conditions of the experiment. 



From the above analysis we see : 



(i) That the phenomenon of phagocytosis can be satis- 

 factorily treated from the physical point of view as a random 

 interfusion between two perfectly intermixed systems of particles, 

 each of which is evenly distributed, in which ingestion takes 

 place when individuals of opposite type have collided. 



(2) That the average content can be calculated from the 

 proportion of leucocytes which remain empty at the conclusion 

 of the experiment, the actual observation involving a minimum 

 of labour. And that this method eliminates, to a large extent, 

 the personal factor of the particular investigator. 



(3) The frequency distribution obtained, and the consequent 

 relation between the average content and the proportion of cells, 

 is independent of <£(t). For example, the same relations will 

 hold good in an experiment conducted at constant temperature 

 and in one in which the temperature has been allowed to vary 

 in any way whatsoever. In other words, the frequency dis- 

 tribution, or the relation between the populations in the various 

 groups, is obtained after the elimination of an unknown 

 chemical law which governs the velocity of reaction, and is 

 thus independent of it. 



