4 HANDBOOK OF PHYSIOLOGY. 



last two In small quantities only. A proteicl-like substance, nuclein, 

 found in the nuclei of cells, contains phosphorus in greater abundance. 

 In cell protoplasm a compound of nnclein with proteid, called nucleo- 

 proteid, forms the most abundant proteid substance. Other bodies are 

 frequently found associated with the proteids, such as glycogcn, starch, 

 cellulose, which contain the elements carbon, hydrogen, and oxygen, the 

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

 hydrates ; fatty bodies, containing carbon, hydrogen, and oxygen, but 

 not in proportion to form water; lecithin, a complicated fatty body con- 

 taining 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 sub- 

 stances. 



The vital or physiological characteristics of protoplasm may be 

 well studied in the microscopic animal called the amoeba, a unicellular 

 organism found chiefly in fresh water, but also in the sea and in damp 



Fig. 3. Phases of aiuoeb id movement. 



earth. These properties may be conveniently studied under the follow- 

 ing heads: 



1. The Power of Spontaneous Movement. When an amoeba is ob- 

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

 irregular mass of protoplasm probably 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 grad- 

 ually thrust out from the main body and retracted; a second mass is 

 then protruded in another direction, and gradually the whole proto- 

 plasmic substance is, as it were, drawn into it. The amoeba thus comes 

 to occupy a new position, and when this is repeated several times we 

 have locomotion in a definite direction, together with a continual change 

 of form. These movements, when observed in other cells, such as the 

 colorless blood-corpuscles of higher animals (fig. 3), in the branched 

 cornea cells of the frog and elsewhere, are hence termed amoeboid. 



The remarkable movement of pigment granules observed in the 

 branched pigment cells of the frog's skin by Lister are also probably 

 due to amoeboid movement. These granules are seen at one time distrib- 

 uted uniformly through the body and branched processes of the cell, 

 while at another time they collect in the central mass leaving the 

 branches quite colorless. 



