FUNCTIONS OF CELLS CELL-CONTENTS. 327 



ferences. The result of an excitation, or if you will, an 

 irritation, may, according to circumstances, be either a 

 merely functional process ; or the effect may be that a 

 more or less increased nutrition of the part is induced 

 without there necessarily being any excitation of its func- 

 tions ; or a formative process may set in, giving rise to a 

 greater or less number of new elements. These differ- 

 ences manifest themselves with greater or less distinct- 

 ness in proportion as the individual tissues of the body 

 are more or less capable of responding to the one or other 

 kind of excitation. When, namely, we speak of the 

 functions of parts in the case of a considerable num- 

 ber of tissues the real functions shrink into a very small 

 compass ; we are on the whole able to say but very little 

 concerning the real functions, in the higher sense of the 

 word, of nearly all the connective tissues, and of the 

 great majority of epithelial cells. We are no doubt 

 able to say what their use under particular circum- 

 stances is, still they always rather appear to be rela- 

 tively inert masses, which scarcely perform any real 

 functions in the ordinary meaning of the word, but 

 rather serve as supports to the body, or as coverings to 

 the different surfaces, or, in other localities, according 

 to circumstances, act as media of union, intervention, or 

 separation. 



The case is different, on the other hand, with those 

 parts, which, owing to the peculiar nature of their inter- 

 nal arrangement, are liable to a more rapid change, 

 such as the nerves, muscles, and muscular organs, glands 

 and a few other structures, as, for example, among the 

 epithelia, ciliated epithelium. In all these tissues, which 

 are subservient to important functions, we find that 

 these functions are chiefly due to very delicate changes 

 of arrangement, or if you wish it expressed in more 

 precise terms, to minute changes of place, in the minute 



