Ch. Ill, ,5] 



protoplas:m 



39 



the \italistic conception of organic nature held by some 

 biologists, and the latter with the mechanistic conception 

 held by others. 



Protoplasm is uniciue in possessing simultaneously two 

 sets of properties, physical and physiological. Its physical 

 properties, — color, den- 



."^. 



Va 



sity, weight, hardness, etc., 

 — are of course simply the 

 aggregate of the proper- 

 ties of its many con- 

 stituent substances. Its 

 physiological properties 

 are those which are pecul- 

 iar to itself as the lining 

 material. They are mani- 

 fest most clearly in the 

 phj'siological processes of 

 plants which they make 

 possible ; and we need 

 here but give, for the 

 sake of completeness, and 

 rather for future reference 

 than present learning, the 

 mere roll of their names, 

 viz. automatism, regula- 

 tion, metaboUsm, mobihty, division, growth, irritabiUty, 

 heredit}', variability, morphological plasticity. 



All protoplasm originates, and therefore all organisms 

 arise, in only one way, so far as known, and that is by 

 growth and di^^sion (or reproduction) of preexisting proto- 

 plasm. Spoxtaneous gexehatiox, or the formation of 

 protoplasm anew out of non-li\'ing materials, is not known 

 to occur an}TT,-here in nature ; for all supposed cases thereof 

 when investigated by scientific methods have been found 

 to be onlj- apparent and not real, as Pasteur was the first to 

 prove. Thus we can trace back all existent li\ing beings 



\ /-" 



Fig. 14. — Portion of the body (Plas- 

 modium) of a Slime-mold ; X 225. Such 

 organisms, which are naked flat masses 

 of protoplasm, often several square inches 

 in area, provide ample material for chem- 

 ical analysis of the substance. (From 

 Sach.s. Lectures.) 



