PROTOPLASM 19 



Protoplasm has therefore been called the "physical basis 

 of life." It may be defined as the active substance of which 

 living things are composed. It is usually colorless, semifluid 

 or gelatinous in consistency, of greater refractive power than 

 water, and granular in appearance. Consisting largely of 

 water, it nevertheless does not mix with water as long as it 

 is living. Its specific gravity is greater than 1 (paramecium, 

 1.25), but varies in many organisms by the formation and 

 disappearance of vacuoles. 



The fluid nature of protoplasm is shown 



1. By the streaming phenomena in plant cells and in the 

 pseudopodia of rhizopods. 



2. By its formation into spherical masses whenever it is 

 freed from its cell walls. 



3. By the assumption of a spherical form by fluids when 

 embedded in a mass of protoplasm. Granules and all foreign 

 substances lie in a ground substance, which at times is perfectly 

 homogeneous, but usually has a structure resembling a network. 



Of the many attempts to explain the finer structure of proto- 

 plasm, that of Biitschli is the most successful. According 

 to this investigator, protoplasm is an emulsion, the vacuoles 

 or globules of which, through mutual pressure, according 

 to well-known mathematical principles, give rise to the appear- 

 ance of a network. The granules, etc., never lie within the 

 vacuoles, but always between them. Biitschli has imitated 

 in every detail the appearance of protoplasm by artificial 

 emulsions. These were prepared by mixing intimately cane 

 sugar or potassium carbonate with old olive oil. A minute 

 quantity of the mixture, placed in a drop of water under the 

 microscope, showed not only all the peculiarities of the proto- 

 plasmic structure, but also spontaneously took on ameboid 

 movements. 



Protoplasm is not a chemical but a morphological term 

 i. e., it does not consist of a definite chemical compound, but 

 of the greatest variety of substances, some of which are the 

 most complicated with which chemists have to deal. It con- 

 tains carbohydrates, fats, water, salts, and always proteins. 

 The elements which are present C, N, H, O, S, P, Cl, K, 

 Na, Mg, Ca, and Fe are all of low atomic weight. Proto- 

 plasm with very few exceptions is divided into microscopic 



