10 



FOUNDATIONS OF BIOLOGY 



appearance in which the alveoli, or ' bubbles, ' represent a more 

 liquid substance emulsified in a less liquid medium. Again, 

 at other times, the denser portion seems to take the form of 



minute rods, or fibers, distributed in 

 a somewhat fluid matrix. (Fig. 3.) 

 These appearances have given 

 rise to various theories which em- 

 phasize one or another as the 

 universal formula for the physical 

 structure of protoplasm, from 

 which the other appearances are 

 merely secondarily derived. But 

 the trend of recent work has been 

 to indicate that although the gen- 

 eral similarity of protoplasmic ac- 

 tivity, wherever we find it, might 

 lead us to expect to find also a 

 visible fundamental structural 

 basis, such does not exist within 

 the range of magnifications at our 

 command. Reticular, alveolar, and 

 fibrillar structures which our mi- 

 croscopes reveal are, as it were, 

 merely surface ripples from underlying physico-chemical 

 changes which, thus far, have proved unfathomable. 



B. CHARACTERISTICS OF LIVING MATTER 



Since the phenomena of life are without exception the 

 results of protoplasmic activity, it is obvious that we must 

 look to protoplasm for the primary attributes of living 

 matter. The properties which are absolutely diagnostic of 

 living matter are its chemical composition, metabolism 

 including the power of waste and repair, growth by intus- 



Fiu. 3. Alveolar appearance 

 of the protoplasm of a cell from the 

 skin (epidermis) of an Earthworm. 

 (From Verworn, after Butschli.) 



