46 INTRODUCTION TO CYTOLOGY 



or part of a protoplasmatic organ, usually the cytoplasm. They may dissolve but 

 do not become protoplasm again. 



3. Ergastic subdances: non-living substances arising anew in or on the protoplast; 

 these correspond to the metaplasm of Hanstein. The intercellular substance, regarded 

 as living by Heidenhain, is held to be ergastic by Meyer. 



Protoplasm and Life. — Huxley, in his famous essay of 1868, very 

 aptly termed protoplasm "the physical basis of life." Since the true 

 significance of protoplasm was first recognized, many suggestions have 

 been ventured regarding the nature of the relation existing between life 

 and its physical basis. The modern conception of protoplasm as a living 

 system was preceded by a number of speculative "micromeric theories," 

 or "atomic theories of biology," according to which the principle of life 

 was held to reside in ultimate vital particles.^- Such fundamental 

 particles were supposed to be for the most part of ultramicroscopic size, 

 capable of growth and reproduction by division, and associated like 

 members of a vast colony in protoplasm. Attempts were also made to 

 account for the activities of protoplasm on the basis of the known chemical 

 reactions of certain of its constituents, notably the proteins. It is not 

 surprising that the peculiar properties of these compounds, which are 

 certainly very significant, should have led to the belief that life is primarily 

 a series of changes in special labile protein molecules, or "biogens" 

 (Verworn). 



The fundamental fallacy involved in all such speculation lies in 

 attributing the properties of a system to some one of its constituent ele- 

 ments and consequently in attempting to draw a sharp line between 

 "living" and "lifeless" components. Sachs (1892, 1895) and many others 

 have urged that the various elements should be referred to as active and 

 passive rather than living and lifeless. It cannot be emphasized too 

 strongly that protoplasm is a living system of components which by them- 

 selves are non-living — a system composed of all the substances that are 

 participating in essential protoplasmic reactions at a given moment (cf. 

 Wilson, 1923). 



The various constituents of protoplasm share in all degrees in deter- 

 mining the activity of the system of which they are integral parts. It is 

 probable that protoplasm always contains visible or invisible materials 

 which might be removed without terminating the life processes. This 

 does not prove, however, that these materials had no share in the processes 

 while they were a part of the system, but shows only that the system which 

 remains after their removal still has an organization permitting it to con- 

 tinue in the living state. It is an altered system and operates in a some- 

 what altered manner. Furthermore, the same chemical compound may 



'2 For summaries of these theories, see Delage (1903), Heidenhain (1907), Kellogg 

 (1907), and Meyer (1920). Some regard the gene theory as a modern development of 

 the same kind. 



