16 



circumstances (as, for instance, hasmoglobin, whether present as a 

 constituent of the blood corpuscles, or dissolved in water, or in the 

 form of crystals). Protoplasm, on the other hand, cannot be 

 placed under different conditions without ceasing to be protoplasm, 

 for its essential properties, in which its life manifests itself, 

 depend upon a fixed organisation. For as the principal attributes 

 of a marble statue consist in the form which the sculptor's hand 

 has given to the marble, and as a statue ceases to be a statue if 

 broken up into small pieces of marble (Nageli II. 28), so a body 

 of protoplasm is no longer protoplasm after the organisation, 

 which constitutes its life, has been destroyed ; we only examine 



the considerably altered ruins of 

 the protoplasm when we treat 

 the dead cells with chemical re- 

 agents. 



It is possible that after a time 

 our knowledge of chemistry may 

 have advanced sufficiently to en- 

 able us to produce albuminous 

 bodies artificially by synthesis. 

 On the other hand, the attempt 

 to make a protoplasmic body 

 would be like Wagner's en- 

 deavour to crystallise out a 

 homunculus in a flask. For, as 

 far as we know at present, proto- 

 plasmic bodies are only reproduced 

 from existing protoplasm, and in 

 no other way ; hence the present 

 organisation of protoplasm is the 

 result of an exceedingly long pro- 

 cess of development. 

 It is very difficult to determine the chemical nature of the sub- 

 stances which are peculiar to living protoplasm. For setting 

 aside the fact that the bodies are so unstable that the least inter- 

 ference with them essentially alters their constitution, the 

 difficulty in analysing them is considerably increased by the 

 presence in each cell of various waste pi-oducts of metabolism, 

 which it is not easy to separate from the rest of the cell contents. 

 Amongst these complex substances the proteids, as the true sus- 

 tainers of the vital processes, are of especial importance ; these 



FIG. 2. Amoeba. Proteus (after Leidy ; 

 from Rich. Hertwig) : n nucleus; cv con- 

 tractile vacuole; n food vacuoles ; en 

 eiidoplasm ; ek ectoplasm. 



