44 THE GENERAL CHARACTERS OF CELLS, BY S. STRICKER. 



for instance, that between the epidermal cells of the fish there 

 are peculiar clavate cells which have been described by Max 

 Schultze, and circular-headed cells by F. E. Schulze; whilst 

 wandering cells, chalice-like cells, etc., have been observed by 

 others. All these forms of cells are probably functionally 

 different, and cannot, according to our ideas of classification, 

 be included under the single head of epidermal cells. 



It has been thought that a primary ground of classification 

 of cells might be drawn from some of their morphological 

 characters or genetic peculiarities, but we shall see that none 

 of these characters are sufficient to attain the end in view. 



In reference to function we must distinguish nerve cells, 

 muscle cells, red blood cells (respiratory organisms), gland or 

 secreting cells, ciliated cells, and, lastly, connective tissue cells, 

 as amongst those whose function essentially consists in the con- 

 struction of the framework of the body. With these may also 

 be enumerated those cells, the function of which we deduce from 

 their situation and arrangement; to this group belong the 

 cells of the epidermis, with the endothelia and those cellular 

 investments of the mucous membranes to which we can ascribe 

 no specific secretion, as the epithelium of the oesophagus and of 

 the urinary tubuli. The function of these may be considered to 

 consist in forming the boundaries of cavities, and in protecting im- 

 portant organs, as the cutis, against external injurious influences; 

 but at the same time we must admit that in regard to their mor- 

 phological differences we are but partially acquainted with their 

 function. Lastly, the colourless lymph and blood corpuscles may 

 be alluded to ; of these we know indeed that in all probability 

 they are destined for the regeneration of the red blood cor- 

 puscles, but we know also that they fulfil other and quite 

 different objects. 



Cells can be classified according to their genesis, that is, 

 according to the germinal membrane from which they origi- 

 nate; nevertheless, however successfully the classification of 

 investing cells into epithelia and endothelia (His) may be 

 effected on this principle, it is not capable of wider applica- 

 tion. The cells of the cutaneous glands, for example, would 

 have to be separated from those of the intestinal glands, because 

 the former proceed from the upper, the latter from the lower, 



