166 DR. E. KLEIN. 



maintains that every epithelial cell, no matter whether in the rete 

 Malpighii, or the laminated epithelium of a mucous membrane, or 

 in gland tubes, is a " prickle-cell/^ i. e. connected with its neigh- 

 bour by fine processes, and that every nucleus of these cells is 

 possessed of processes — that is to say, is a " prickle-nucleus " 

 (Stachelkern), and the nucleolus of each of these ^^prickle- 

 nuclei" is similarly constituted, i. e. is a "prickle-nucleolus '^ 

 (Stachelkernkorperchen). In the foregoing pages I have several 

 times mentioned the relation and value of what is generally de- 

 scribed as a nucleolus to the rest of the nucleus, and we have 

 seen that its nature is in many instances a very doubtful one, and 

 its occurrence variable and inconstant, and I cannot therefore 

 accept what Heitzmann says of this pseudo-organ. Nor can I 

 agree to the proposition that all epWiellal cells, no matter 

 where they are found, are " prickle- cells /^ 



There is one other point which I have to mention in connec- 

 tion with the cells of the laminated epithelium of those parts 

 which are capable of being placed in folds, e. g. skin, cESophagus 

 and pharynx. It is this, that the shape of the cells of the deeper 

 and middle strata may be entirely altered by the different con- 

 dition of contraction of the subjacent membrane. If, for instance, 

 a small piece of the above organs, while being hardened in spirit 

 or chromic acid, is left altogether to itself, it will shrink into 

 folds to a considerable degree. In vertical sections through 

 these structures the rete Malpighii, or the laminated epithelium 

 respectively, is found to present a different aspect on and between 

 the folds, inasmuch as in the former instance the epithelial cells 

 of both the middle and deeper strata possess an elongated shape, 

 their long axis being parallel to the vertical diameter; in the 

 parts between the folds the epithelial cells, on the contrary, are 

 more elongated in the horizontal direction, i. e. are more 

 flattened. But if during the hardening those membranes are 

 prevented from an excessive shrinking by fixing them on cork or 

 bone or cartilage, the shape of the cells of the above-named layer 

 will be found of the typical character which is generally ascribed 

 to them, viz. the deepest cells more or less columnar, the follow- 

 ing ones more or less polyhedral, gradually becoming flattened 

 as the surface is approached. And for this reason the rete 

 Malpighii of the epidermis of the ear-lobe, for instance, appears 

 different from that of ordinary skin that had been allowed to 

 shrink during hardening ; in the former, where the skin is pre- 

 vented from shrinking by being fixed on the cartilage, the rete 

 Malpighii is of tlie typical appearance ; in the latter the cells of 

 the middle and deeper stratum of the folds are very much elon- 

 gated in a vertical direction. 



In connection with this change of shape we also see that the 



