THE LEUCOCYTES IN ORGANIC FUNCTIONS. 715 



having demonstrated their presence in the alveoli. Again, the 

 path for these leucocytes from the intestine to the true respira- 

 tory areas of the lungs is comparatively direct: features which 

 distinctly suggest that the protective functions in the respira- 

 tory tract resemble those in the intestinal canal, as regards the 

 eosinophilic granules and the phagocytic functions of the neu- 

 trophiles, both kinds of cells being present, as we have seen. 

 Of course, the intestinal lymph-follicles being the source of 

 these cells, another arrangement prevails in the pulmonary 

 lobules: i.e., that to which we referred on page 713, to the effect 

 that the lobular epithelium per se is an aggregate of neutro- 

 philes and eosinophiles. 



We can readily understand, now, why the eosinophiles de- 

 plete themselves of their granules in the alveoli: i.e., to dis- 

 solve them in the plasma prior to their absorption by the red 

 corpuscles. Indeed, the reticular structure of red corpuscles, 

 "the same as that of colorless blood-corpuscles," 47 observed 

 by Louis Elsberg in 1879, seems to us to present all the feat- 

 ures that have led us to consider as canaliculi the threads that 

 constitute this reticulum in the latter cells. That the red- 

 corpuscle "granulations," "platelets," or "haematoblasts" de- 

 rived from them are mere droplets of oxidizing substance 

 poured out through these canaliculi is shown by the fact that 

 the characteristic affinity (requiring oxygen and alkaline salts, 

 according to Ehrlich) for methylene-blue again appears: i.e., 

 as manifested by the deep-blue stain which we found in other 

 structures, the axis-cylinder, neuroglia, etc., and in the leuco- 

 cytes themselves. This fact was also noted by Litten. 48 That 

 the droplets pass out through centrifugal channels in the cell, 

 and that the latter presents the general mechanical character- 

 istics of leucocytes, is also suggested by the researches of 

 Hirschfeld, 49 who observed that the "blood-plates" are first 

 seen as circular disks occupying the center of the cell, then 

 move very slowly toward the periphery, and finally drop out 

 of the cell through a minute aperture, which closes up again. 



* 7 M. L. Holbrook: "Proceedings of the American Microscopical Society," 

 vol. 1894. 



"Litten: Deutsche med. Wochenschrift, Nov. 2, 1899. 

 "Hirschfeld: Virchow's Archiv, vol. clxvl, 1901. 



