16 LIVING AND LIFELESS MATTER 



are accordingly either morphological or physiological. (See 

 Chapter IX.) 



These properties, chemical composition, power of waste and 

 repair, growth by intussusception, power of reproduction and 

 adaptability are primary attributes of protoplasm, and serve to 

 distinguish living from all other kinds of matter. It does not 

 follow, however, that non-living things do not manifest one or 

 more of these phenomena. Thus the chemical composition, 

 as we have seen, is that of lifeless protein, while growth by 

 intussusception may be said to take place whenever a solid 

 crystalloid is dissolved in a liquid. Furthermore these proper- 

 ties are of such a nature that if we were dependent upon them it 

 would be difficult in some cases to tell whether an organism is 

 alive or not. To determine its chemical composition it would 

 have to be killed; its growth, waste and repair could not be 

 easily observed, while only a fortunate chance would reveal its 

 reproduction. It is possible, however, to determine by certain 

 characteristics of protoplasm whether a given thing is living 

 matter or not without the necessity of ascertaining its prop- 

 erties, and these we speak of as the evidences or manifestations 

 of vitality. 



These are usually included under the heads of appearance, 

 form and movement. 



PROTOPLASMIC APPEARANCE. Under a microscope, proto- 

 plasm has a characteristic and recognizable appearance not 

 easy to describe. If seen with a low magnification it appears 

 like a transparent, colorless, somewhat glass-like, semi-fluid 

 substance usually with numerous granules of variable size and 

 with many clear spaces or vacuoles. It is always refringent 

 and never mixes with the surrounding water. It is viscous; 

 has a high power of cohesion and readily absorbs substances 

 by osmosis from the surrounding medium and gives off sub- 

 stances, also by osmosis, to the surrounding medium. It is, 

 therefore, permeable in respect to some substances. If seen 

 under a high magnification the appearance differs with the ob- 

 ject. In some cases there is a more or less definite reticulum 

 or network enclosing a more fluid substance; in other cases the 



