THE LEUCOCYTES IN ORGANIC FUNCTIONS. 707 



observation, however, adds another link to the chain of evi- 

 dence which unites the eosinophiles to the neutrophiles, for, 

 in addition to being both nucleo-proteid carriers, they now 

 become also iron-carriers. By tracing the itinerary of this iron 

 we may, therefore, obtain a clue to the true identity of its 

 cellular host. 



The phagocytes seen by Macallum to ingest the albuminate 

 of iron, being assimilated to those charged at all times with 

 the duty of selecting proteids from the intestinal foodstuffs, it 

 becomes a question as to where they can part with their iron 

 in order to facilitate its absorption into the haemoglobin mole- 

 cule, of which, as is well known, it forms an important con- 

 stituent. From the intestine the iron is carried to the portal 

 system, thence into the hepatic lobule. It must be here that 

 the phagocytic leucocytes must take part in some process re- 

 lated to the elaboration of hemoglobin, for we have seen on 

 page 335 that in the spleen the leucocytes are formed in situ, 

 pass out into the pulp-tfhannels, take up the iron-pigment 

 (probably that of disorganized red corpuscles), and carry it to 

 the liver. Again, and for reasons which are there given, we 

 were led to conclude (page 339) that bilirubin and iron were 

 used to build up the hemoglobin in the lobular (hepatic) capil- 

 laries. The liver, therefore, seems to receive iron from both 

 directions intestine and spleen a normal mechanism when 

 we consider that the liver's blood passes almost directly to the 

 heart, and thence to the lungs. 



How do the eosinophile (non-phagocytic) leucocytes ac- 

 quire their iron? We can hardly imagine that when the splenic 

 or intestinal leucocytes reach the hepatic lobule their contents 

 or any part thereof is disgorged to enable another cell to ap- 

 propriate it. Indeed, there is not the slightest evidence that 

 such a process occurs, although the eosinophile has already 

 been shown to contain not only iron, but also the other main 

 constituents of the neutrophile cell. There exists a physiolog- 

 ical process, however, through which the eosinophile can ac- 

 quire all the attributes of the latter: i.e., by mitosis, a mode 

 of cell-multiplication known to apply to leucocytes and par- 

 ticularly to neutrophiles. Gulland refers to this feature in the 

 following lines: "The cells which one sees dividing or about 



