104 M. ARMAND BUFFER. 



dermic structures of higher animals have similar functions. 

 A few instances will suffice to illustrate this. 



When the tadpole passes into the frog stage, the muscles and 

 nerves of the tail gradually disappear as they become a prey 

 to amoeboid cells, which surround them and eat up the tissue 

 which still presents the structure of normal muscular fibres. 

 This process is precisely similar to that which Kowalevsky 

 has observed during the metamorphosis of flies. 



Again, amceboid mesodermic cells collect round the muscles 

 of the tail of living, uninjured Bombinator larvae^ at the be- 

 ginning of the metamorphosis, and gradually devour these 

 structures. During the progress of the atrophy of the gills 

 also, the presence of large fully-laden mesodermic cells may be 

 easily demonstrated. 



The mesodermic cells of higher Vertebrata have similar 

 functions. The resorption of osseous substance" constantly 

 taking place in the shaft of long bones is essentially dependent 

 on the presence of large multinucleated cells (Osteoclasts, 

 Myeloplaxes of Robin), which excavate small shallow pits 

 (foveolse) in the part which is undergoing absorption. 



Large mono-nucleated cells containing red blood-corpuscles 

 in their interior are also met with in the spleen.^ These intra- 

 cellular red blood-corpuscles may be normal in appearance, 

 but more frequently they appear to be disintegrated and 

 digested in the interior of these large spleen-cells, a few 

 pigment-granules representing all that remains of them. Many 

 observers have succeeded in watching the process of intra- 

 cellular digestion of red blood-corpuscles actually taking place. 



Mesodermic cells not only devour other structures, but prey 

 on one another also. According to Heidenhein, the walls of 

 the intestinal canal of certain animals,* more especially guinea- 

 pigs, are lined by epithelium cells, between which large 

 mesodermic cells find their way to the surface and absorb 



• Metscbnikoff, 'Quart. Journ. of Micr. Sci.,' vol. xxiv, p. 112. 



' Kolliker, ' Die normale usorption des Kuochengewebes,' Leipzig, 1873. 



3 Bardacb, 'Ann. de I'Institut Pasteur,' Dec, 1889, p. 599. 



"• Heidenhein, 'Pfliiger's Archiv,' vol. xlvii, 1888. 



