2*5 



IV. THE ELEMENTARY PART, UNIT, OR CELL, 

 AND OF THE FORMATION OF TISSUE. 



THE reader will have gathered from what has been already 

 said, that the word " cell," which was originally restricted 

 to a body having an envelope or wall closed at all points, 

 has been also used, especially of late years, in speaking of 

 bodies destitute of any such structure. Moreover, the 

 views concerning the way in which it was supposed, at the 

 time the word " cell " came into use, that the cell-wall was 

 formed, have been shown to be erroneous, and the action 

 and significance of the so-called cell-wall, have been found 

 to be entirely different from what was supposed at the time 

 of the discovery of the cell. Now, during the early stages 

 of development of every " cell," there is no vestige of any 

 structure to which the term cell-wall could be properly 

 applied. Nevertheless, very small particles of living matter 

 have been termed cells, and authors have included in their 

 cell category, structures devoid of the parts, and destitute of 

 the characters which they themselves had asserted to be ne . 

 cessary to the cell. White blood corpuscles and other naked 

 masses of bioplasm have been called " cells ;" and it has 

 been already stated (page 204), that the last new name 

 coined for the designation of these bodies was " leucocyte " 

 or white cell. Students have, of course, been misled by 

 this term, for when they looked for themselves at the body 



