PART II 



THE PHYSICAL STATES OF PROTOPLASM 

 AT LOW TEMPERATURES 



A substance may exist in four states, as a gas, as a 

 liquid, as a crystal and as a glass. The relation between 

 these states and temperature is illustrated in the diagram 

 (Fig. 1), in which the temperatures are plotted on a hori- 

 zontal axis, with the absolute zero at the origin. "A body 

 is a gas at high temperatures, in the zone A ; it is a liquid 

 at lower temperatures, in the zone B ; it becomes crystalline 

 at still lower temperatures, in the zone C ; and it hardens, 

 but does not crystallize, that is, it takes the vitreous state, 

 if it is brought (^\dthout being previously crystalline) to 

 the low temperatures represented by the zone D. ' ' (Luyet, 

 1937, p. 1). 



D , C , B , A 



A.Z. R Q P 



Fig. 1. Diagram representing the relationship between temperature and 

 the four states of matter. A.Z. : Absolute zero. 



Some physicists (cf. Tammann, 1925, p. 2) for whom the 

 arrangement of the molecules in the aggregate is the essen- 

 tial feature in the detinition of the states of matter, name 

 only two of them : the crystalline state which possesses as a 

 specific character an ordered arrangement of the atoms, 

 and the amorphous state (gas, liquid and vitreous) in which 

 the molecules are distributed at random in space. Most 

 students of nature name three states : gas, liquid and solid, 

 and make of the vitreous state a subdivision of one of the 

 three. Some, considering the fact that a glass possesses 

 the hardness and cohesion of the solid bodies, classify it as 

 a form of the solid state ; others, considering the def orm- 

 ability presented by some glasses during long periods of 



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