106 M. AEMAND BUFFER. 



found in the intestinal canal, says, "Now there does not 

 appear a doubt that these large giant-cells are developed from 

 the ordinary lymphocytes," and proceeds to give figures 

 showing their gradual development. In the writer's paper on 

 the "Phagocytes of the Alimentary Canal/' ^ he showed that 

 the Macrophages of the Peyer's patches and tonsils are derived 

 from small lymphocytes, and he described the mode of deve- 

 lopment of these enormous cells. In the spleen-pulp and 

 venous sinuses of the same organ also the writer has been 

 able to trace the development of the Macrophages from Micro- 

 phages, for all intermediate stages between them can easily be 

 observed. 



It has been shown that the mesodermic cells of invertebrata 

 not unfrequently come to the surface, scavenge the outside of 

 the animal's body, and remove any dead particles which they 

 may come across. In vertebrata the same process takes place in 

 the mucous membranes lining the cavities of the body which 

 are in contact with the external world. Eberth^, as early as 

 1864, noticed that wandering cells force their way between the 

 epithelium cells covering the intestinal canal. Ph. Stohr^ then 

 drew general attention to the fact that this emigration takes 

 place along the whole length of the alimentary tract. The 

 writer has shown that the leucocytes of dogs wander to the 

 free surface of the tonsils, take particles of dust, charcoal, 8c6., 

 into their interior, and carry them into the depths of these 

 organs. Here the Microphages and their contents frequently 

 fall a prey to the Macrophages present in these structures. This 

 fact proves that the mesoblastic cells of vertebrata have func- 

 tions similar to those of invertebrata, but evidence far more 

 conclusive can be obtained by observing what takes place in 

 the lungs of various animals. 



Particles of charcoal, dust, &c., are to be met with in the 

 epithelioid cells (Saub zellen) of the lungs of most animals. 

 The precise nature of these cells remained uncertain until the 



1 Armand Ruffer, loc. cit. 



' Ebertli, ' Hiirzburger Naturwissenschaft. Zeitschrift,' 1804, p, 23. 



' Ph. Stolir, see Heidenhein, loc. cit. 



