CHARACTERISTICS OF PROTOPLASM 3 



fluid. These vacuoles are more numerous and pronounced in vegetable than 

 in animal cells. Gas bubbles also sometimes exist in cells. 



It is impossible to make any definite statement as to the exact chemical 

 composition of living protoplasm, since the methods of chemical analysis 

 necessarily imply the death of the cell; it is, however, stated that protoplasm 

 contains 75 to 85 per cent of water, and of the 15 to 25 per cent of solids the 

 most important part belongs to the class of substances called proteids or al- 

 bumins. Proteids contain the chemical elements carbon, hydrogen, nitrogen, 

 oxygen, sulphur, and phosphorus, the last two in very small quantities only. 

 A proteid-like substance, nuclein, found in the nuclei of cells, contains phos- 

 phorus in greater abundance. In the cell nucleus a compound of nuclein 

 with proteid, called nucleoproteid, forms the most abundant proteid sub- 

 stance. Other bodies are frequently found associated with the proteids, such 



FIG. 3. Phases of Ameboid Movement. 



as glycogen, starch, cellulose, which contain the elements carbon, hydrogen, and 

 oxygen, the last two in the proportion to form water, and hence are termed 

 carbohydrates; fatty bodies, containing carbon, hydrogen, and oxygen, but not 

 in proportion to form water; lecithin, a complicated fatty body containing 

 phosphorus; cholesterin, a monatomic alcohol; chlorophyll, the coloring matter 

 of plants; inorganic salts, particularly the chlorides and phosphates of calcium, 

 sodium, and potassium; ferments, and other substances. 



The Physiological Characteristics of Protoplasm. The properties 

 of protoplasm may be well studied in the microscopic animal called the 

 ameba, a unicellular organism found chiefly in fresh water. These properties 

 may be conveniently studied under the following heads: 



The Power of Spontaneous Movement. When an ameba is observed 

 with a high power of the microscope, it is found to consist of an irregular mass 

 of protoplasm containing one or more nuclei, the protoplasm itself being 

 more or less granular and vacuolated. If watched for a minute or two, an 

 irregular projection is seen to be gradually thrust out from the main body; 

 other masses are then protruded until gradually the whole protoplasmic sub- 

 stance is, as it were, drawn over to a new position, and when this is repeated 

 several times we have locomotion in a definite direction, together with a con- 

 tinual change of form. These movements, figure 3, when observed in other 

 cells, such as the colorless blood-corpuscles of higher animals, in the branched 

 corneal cells of the frog and elsewhere, are termed ameboid. 



