16 E. A. Schäfer, 



push their pseudopodial processes into the mucus which Covers the 

 surface, or whether they may occasionally pass bodily out into it I am 

 imable positively to say. In some parts they occur in great numbers, 

 as in the case of the epithelium which Covers the lymphoid tissue of 

 the solitary and agminated glands, and they are scarcely ever entirely 

 ahsent from the epithelium. They often appear to be nested together 

 to form small clumps of three or more cells, not improbably 

 derived from the division of a single cell; and indeed it is often dif- 

 ficult in sections to decide whether it is really a clump of several 

 cells or a larger multi-nucleated cell which is under Observation. 



The amoeboid cells in the epithelium appear to be considerably 

 more numerous during absorption than at other times : tliis is distinctly 

 Seen in the frog : and they then seem also to approach nearer the sui'- 

 face. They may also be very abundant at the base of the epithe- 

 lium between this and the basement membrane; as is most evident 

 when, in consequence of the violent contraction of the muscular flbres, 

 the tissue of the villus becomes retracted and dragged away from the 

 epithelium, leaving a space between in which may be seen many 

 lymph-corpuscles. Lastly, lymphoid cells occur in the lacteals them- 

 selves, where they are seen in sections suspended in the coagulated 

 lymph, but they are found much more numerously in the lacteals of 

 the villi than in those which are more deeply seated, and most nu- 



as in that of tlie stomach, of the pharjoix, of the trachea and brouchi, and even 

 free within the alveoli of the lungs, it may fairly be replied that these are all ab- 

 sorptive surfaces although to a variable degree; and in the case of those amoeboid 

 cells which are seen in the alveoli of the lung and which take up any carbon 

 particles which may reach the alveoli with the air inspired, it can be shown that 

 many of them pass again into the tissue of the lung and carry vdth them the 

 incepted carbon particles into the lymphatics. No doubt many of the cells which 

 penetrate the epithelium, especially over exclusively lymphoid structures like the 

 tonsils, pass out at the free surface and there appear as mucous and salivary cor- 

 puscles — a fact long known, but recently drawn attention to more particularly 

 by Stöhr (Über Mandeln n. Balgdrüsen, Virch. Arch. XCVII, 2, 1884). But this 

 extrusion is much more marked under pathological than under normal conditions; 

 and it may well be regarded as incidental merely to the presence of those cells in 

 the epithelium, the desquamation of its superficial layers being necessarüy accompanied 

 by the liberation of such cells. 



