CONCERNING PROTOPLASM. 63 



would hardly have contained even the convenient Angels of the 

 Schoolmen, whose ability to accommodate themselves within the 

 limits of the minute is matter of common knowledge still the 

 extension of biological knowledge concerning lower organisms has 

 been fraught with importance in certain easily discernible ways. If 

 we have not been enabled to shout out " Eureka " to the waiting 

 xaces of to-day, we have nevertheless gained some useful ideas re- 

 garding the true directions in which our difficulties must be attacked. 

 Through the comprehension of what the lowest animals and plants 

 are, we have been led to form certain reasonable ideas concerning 

 what life may be. The knowledge of the conditions required to 

 perpetuate the normal existence of living beings, has led us to recog- 

 nise, in some measure, the true nature and extent of the problem 

 that awaits the fuller knowledge of coming years for its solution. 

 Let us, therefore, in the first place, endeavour briefly to gain some 

 adequate ideas concerning the conditions or environments demanded 

 for the exhibition of life in its lowest grades; since, haply, we may find 

 in such a study a clue which may lead us towards the understanding, 

 in theory at least, of the nature of the forces which make and 

 control the living organism. One of the first decided steps towards 

 the simplification of a theory of life was taken when the living con- 

 tents of vegetable cells were discovered to present a striking 

 similarity to the substance representing the essentially living part of 

 the cells of animals. Mulder thus recognised the vegetable pro- 

 toplasm, as he termed the soft, gelatinous matter of the vegetable 

 cell; and Remak in turn described the animal " protoplasm." Need- 

 less to remark that this substance, described as locked up within the 

 cells or units composing the tissues of the higher organism animal 

 or plant and as constituting the active or vital parts of every living 

 being, was identical with the matter, closely resembling white of egg 

 in appearance, which Dujardin had named "sarcode," and of 

 which the bodies of the lowest animals are entirely composed. Max 

 Schultze had indeed shown that the protoplasm of animals was 

 chemically and microscopically indistinguishable from that of plants; 

 and that beneath the variations of form, and the diversities of life, 

 there thus remained a curious uniformity of substance in living 

 organisms. The life and growth of the animal was seen to depend 

 on a substance which was apparently identical with that consti- 

 tuting the living basis of the plant. A curious community of sub- 

 stance was thus proved to underlie wide and apparently irreconcil- 

 able differences of life and habit ; and out of this primary fact grew 

 new and bolder conceptions of the nature of life than had before 

 been ventilated by biologists at large. 



To appreciate clearly and fully what is implied by the statement 

 that the substance now widely known as " protoplasm " is a sine qua 



