1894] The Action of Leucocytes Toward Foreign Substances. 321 
the leucocytes to the spleen cells at once arose. It was already 
proved that no free carbon entered the blood circulation. Con- 
sequently the spleen cells must have obtained their foreign 
material either directly or indirectly from the already ingested 
leucocytes in the blood. Two ways are open for this to take 
place. The leucocytes may in some manner discharge their 
load, which is afterwards taken up by the spleen cells, or the 
spleen cells may ingest the leucocytes and consequently the 
carbon. The latter seems to be the most plausible explanation. 
Moreover from the amount of carbon contained in the spleen 
cells the number of leucocytes destroyed in this manner must 
be considerable. 
A brief summary of the results of the experiments is con- 
tained in the following statements: 
1. No free carbon was present in any part examined. 
2. All carbon was contained in leucocytes except in the 
spleen, where true splenic cells also contained it. 
= 3. Ingested cells were both extra- and intravascular, except 
in the liver. 
4. Ingested cells were free on mucous and epidermic surfaces ; 
in the stomach, lungs and skin. 
5. Ingested cells were in excretory organs with waste pro- 
ducts, kidneys. 
From the above results it is seen that the number of leuco- 
cytes in the body suffers a constant loss in three ways, by the 
wandering out of the cells on mucous and epidermic surfaces, 
by passing away with waste products and through ingestion by 
the splenic cells. The large numbers found in all three con- 
ditions show that the destruction of leucocytes through these 
ways is by no means insignificant. Moreover as no patholog- 
ical conditions, so far as could be determined, were induced in 
the animals by the treatment, there is no reason to believe this 
loss to be other than a normal occurrence. 
This method of removing the artificially introduced material 
by the leucocytes suggests at least the manner of the removal 
of any foreign matter that may enter the circulation during 
life. The leucocytes thus perform the duties of scavengers of 
the body in addition to their other important duties, even if by 
