1893.] MICROSCOPICAL JOURNAL. 335 



bender). In these animals the abdominal cavity forms a great 

 lymph space, the leucocytes in the lymph ingest the carbon and 

 then pass into the blood circulation with the passage of the 

 lymph. The time required for this varied from 6-9 days. In 

 Necturus, owing to the presence of external gills the time of the 

 appearance and disappearance of the carbon could be deter- 

 mined with fair accuracy. In 6-9 days carbon-laden cells ap- 

 peared in the blood and even after 16 days a fevv scattered ones 

 remained. 



In the microscopical examination of the tissues, the presence 

 of large masses of natural black pigment was a great difficulty. 

 After some experimentation this was found to be easily removed 

 by the use of hydrogen dioxide. The serial sections, when cut 

 and fastened to the slide, were put in a vial of the liquid and in 

 Jrom 6-48 hours the color was entirely removed. B}' placing the 

 vials in the sunlight the action is hastened. The decoloriza- 

 tion can be stopped at any point and it was found to be very 

 useful to leave enough yellow color to mark the position of the 

 pigment cells. 



The study of serial sections of the different part-s, showed the 

 ingested cells to be present in the spleen, kidneys, ureters, liver, 

 lungs, stomach, muscle and skin. The disttibution differed 

 somewhat in these parts. In the liver no ingested cells occurred 

 outside the blood vessels. In the kidneys they were in the blood 

 vessels, urinary tubercles, nephrostomes and lyfnph spaces 

 about the glomeruli. In sections made of the ureters close to 

 their entrance into the cloaca, large masses of ingested cells were 

 present. In the stomach, lungs, and skin substantially the same 

 distribution existed. The carbon-laden leucocytes were in the 

 blood vesse s,in the various tissues of the different organs, in the 

 epithelial and epidermal layers and finally free on the inner sur- 

 face of the stomach and lun^s, and on the outer surface of the 

 skin. No trace of free carbon or carbon in any cells besides leu- 

 cocytes ai)peared in these parts 



But when the spleen is considered some very interesting dif 

 fert-nces become apparent. Here the true spleen cells also con- 

 tain carbon scattered about in the cell-body in quite a peculiar 

 way. At first sight, owing to the extended condition of the cells, 

 the carbon appeared to be free in the tissues, but careful exami- 

 nation proved it to be in the spleen-cells. 



