CHAPTER IV 



PROTOPLASM AND THE AMCEBA. 

 PROTOCOCCUS 



Constitution and Structure of Protoplasm. — The vis- 

 cous but semi-liquid mobile protoplasm that forms 

 the bulk of many animal and plant cells is to be regarded 

 as a mixed colloid sol. The continuous phase is water 

 in which various organic and inorganic substances 

 are dissolved. These solutes may vary to a consider- 

 able extent according to circumstances. The disperse 

 phase we believe to consist essentially of ultramicro- 

 scopic particles of protein, which may possibly include 

 separate protein molecules, as well as aggregations of 

 molecules. Fats or fat-like bodies may also exist as 

 part of the disperse phase, and these may be closely 

 associated with the protein droplets. In this sol 

 numerous chemical and physical processes are con- 

 stantly taking place, and it is the sum of these that 

 give rise to the chemical phenomena of life. 



Besides the ultramicroscopic disperse particles, which, 

 together with the continuous watery phase, form, so 

 far as we can tell, the ultimate structural basis of living 

 protoplasm as a form of matter, the protoplasm ordinarily 

 contains much larger microscopically visible granules 

 and droplets of very various size and very various com- 

 position. The presence of these last, like that of the 

 solutes, depends upon the state of the cell in regard to 

 nutrition, etc. The sum total of the chemical processes 



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