CHAPTER I 



GENERAL SKETCH OF THE CELL 



" Wir haben gesehen, dass alle Organismen aus wesentlich gleichen Theilen, namlich aus 

 Zellen zusammengesetzt sind, dass diese Zellen nach wesentlich denselben Gesetzen sich 

 bilden und wachsen, dass also diese Prozesse iiberall auch durch dieselben Krafte hervorge- 

 bracht werden miissen." Schwann. ^ 



The term " cell " is a biological misnomer ; for whatever the living 

 cell is, it is not, as the word implies, a hollow chamber surrounded by 

 solid walls. The term is merely an historical survival of a word 

 casually employed by the botanists of the seventeenth century to 

 designate the cells of certain plant-tissues which, when viewed in 

 section, give somewhat the appearance of a honeycomb.- The cells 

 of these tissues are, in fact, separated by conspicuous solid walls 

 which were mistaken by Schleiden, unfortunately followed by 

 Schwann in this regard, for their essential part. The living sub- 

 stance contained within the walls, to which Hugo von Mohl gave 

 the n3.Vi\Q protoplasm^ (1846) was at first overlooked or was regarded 

 as a waste-product, a view based upon the fact that in many im- 

 portant plant-tissues such as cork or wood it may wholly disappear, 

 leaving only the lifeless walls. The researches of Bergmann, 

 Kolliker, Bischoff, Cohn, Max Schultze, and many others, showed, 

 however, that some kinds of cells, for example, the corpuscles of 

 the blood, are naked masses of living protoplasm not surrounded bv 

 walls, — a fact which proves that not the wall, but the cell-contents, 

 is the essential part, and must therefore be the seat of life. It was 

 found further that with the possible exception of some of the lowest 

 forms of life, such as the bacteria, the protoplasm invariably contains 

 a definite rounded body, the nucleus,'^ which in turn may contain a still 



^ UnteisHchungen, p. 227, 1839. 



- The word seems to have been first employed by Robert Hooke, in 1665, to designate 

 the minute cavities observed in cork, a tissue which he described as made up of " little 

 boxes or cells distinct from one another" and separated by solid walls. 



^ The same word had been used by Purkyne some years before (1840) to designate the 

 formative material of young animal embryos. 



■* First described by Robert Brown in 1833. 



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