214: PEOTOPLASM. 



Contiguous micellae in any organized substance, for instance 

 cell-wall or starch, frequently possess different chemical charac- 

 ters, as is shown by the fact that from such a substance one por- 

 tion can be taken without materially disturbing the external form. 



689. By means of the changes which go on in the formation 

 of new micellae, and in their reconstruction, it is sought to account 

 for the nutrition, growth, and movements of organized substances. 

 This is essentially the basis on which Engelmann^ founds his 

 explanation of the movements of protoplasm.'^ 



590. Continuity of protoplasm. It was supposed until recently 

 that the protoplasm in one young cell is completely shut off from 

 that in contiguous cells by an imperforate cell-wall, and that even 

 in the cases where the wall is perforate there is no communi- 

 cation of protoplasm through the pores. There is abundant 

 evidence to show the incorrectness of this view. In some cases 

 the protoplasm in one cell is practically continuous with that in 



1 Hermann's Handbuch der Physiologie, i. 1879, p. 374. 



2 The application of this hypothesis by Sachs is given somewhat fully in 

 the following extract (Text-book of Botany, 2d Eng. ed., 1882, p. 666) : 

 "Chemical compounds of the most various kinds meet between the micellae 

 of an organized body, so that they act upon and decompose one another. It 

 is certain that all growth continues only so long as the growing parts of the 

 cell are exposed to atmospheric air ; the oxygen of the air has an oxidizing 

 effect on the chemical compounds contained in the organized stracture ; with 

 every act of growth carbon dioxide is produceil and evolved. The equilibrium 

 of the chemical forces is also continually disturbed by the necessary production 

 of heat ; and this may also be accompanied by electrical action. The move- 

 ments of the atoms and molecules within a growing organized body represent 

 p definite amount of work, and the equivalent forces are set free by chemical 

 changes. The essence of organization and life lies in this : — that organized 

 structures are capable of a constant internal change ; and that, as long as. they 

 are in contact with water and with oxygenated air, only a portion of their forces 

 remains in equilibrium even in their interior, and determines the form or frame- 

 work of the whole ; while new forces are constantly being set free by chemical 

 changes between and in the molecules, which forces in their turn occasion 

 further changes. This depends essentially on the peculiarity of mioellar struc- 

 ture, which permits dissolved and gaseous (absorbed) substances to penetrate 

 from without into every point of the interior, and to be again conveyed out- 

 wards. Neither the chemical nor the molecular forces are ever in equilibrium 

 in the protoplasm ; the most various elementary substances are present in it in 

 the most various combinations ; fresh impulses to the disturbance of the Internal 

 equilibrium are constantly being given by the chemical action of the oxygen 

 pf the air ; and energy is continually being set free at the expense of the proto- 

 plasm itself, which must lead to the most complex actions in a substance of so 

 complicated a structure. Every impulse from without, even when impercep- 

 tible, must call forth a complicated play of internal movements, of which we 

 are able to perceive only the ultimate effect in an external change of form." 



