CHAPTER II 



THE CHEMICO-PHYSICAL AND MORPHOLOGICAL PROPERTIES OF 



THE CELL 



The cell is an organism, and by no means a simple one, being built 

 up of many different parts. To ascertain with accuracy the true 

 nature of all these constituents, which, for the greater part, elude 

 our observation at present, will remain a problem for biological 

 research for a long time. Our position, with regard to the cell, is 

 similar to that of investigators towards the whole animal or vege- 

 table body a hundred years ago, before the discovery of the cell 

 theory. In order to penetrate more deeply into the secrets of the 

 cell, optical instruments, and, above all, methods of chemical 

 examination, must be brought to a much higher degree of perfec- 

 tion than they have attained at present. It seems best to me to 

 lay stress on these points to start with, in order that the student 

 may have them always before his mind's eye in reading the follow- 

 ing account. 



In each cell there is invariably to be seen one specially well- 

 de lined portion, the nucleus, which throughout the whole of the 

 animal and vegetable kingdom is very uniform in appearance ; 

 evidently the nucleus and the remaining portion of the cell have 

 different functions to perform in the elementary organism. Hence 

 the examination of the chemico-physical and morphological proper- 

 ties of the cell becomes naturally divided into two sections, the 

 examination of the protoplasm and of the nucleus. 



To these, three short sections are added. The first deals with 

 the question, Are there cells which possess no nuclei ? The 

 second treats of the pole or central corpuscles, which are at times 

 found as special cell-structures in addition to the nucleus ; and in 

 the third a short account is given of Niigeli's theory of the mole- 

 cular structure of organic bodies. 



I. The Chemico-physical and Morphological Properties 



of the Protoplasm. Some animal and plant-cells appear to 



differ so much from one another as to their form and contents, 



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