THE LIVING SUBSTANCE. 9 



Biitschli has not called attention to these film appearances, 

 but they are very uniformly present, and to be made out with 

 greater or less ease as other conditions may allow. In his 

 figures they are probably to be understood in many places 

 where mere breaks in the optical network are given. In the 

 living substance also, similar breaks in continuity of an optical 

 network are seen constantly, without any other image indicating 

 substance. 



[7] Not only is a structure akin to that described and figured 

 by Biitschli found, as he asserts, everywhere in living proto- 

 plasm ; but the facts go even beyond his assertion ; for the 

 substance of his reticulum, that is the "lamellar" and pellicular 

 substance, is found to be itself alveolated ; and to have the 

 physical form of a visco-fluid foam. 



This secondary structure is most often visible on pellicular 

 surfaces, where it is seen as a delicately blistered, or " sha- 

 green" surface, or as delicate striation lines ^; yielding at times, 

 with adjusted focus, a network whose meshes are but one- 

 sixth to one-twelfth the diameter, as to alveoli, of those of 

 Butschli's structure. A pellicle frequently offers room for sev- 

 eral layers of such minute alveoli, yet because of their optical 

 smallness, I have not seen in a pellicle, more than one layer.^ 

 In the meshes proper, the secondary structure sometimes ap- 

 pears as granulation, or vesiculation, or as delicate striation; 

 which there, as well as in the pellicles, may be stable, inter- 

 mittent, or rhythmical. 



The secondary structure is also seen in protoplasmic films, or 

 in extensions from the network of Biitschli, which are, as to 

 their whole mass, less than ^ \i. In such cases there is 



or of smooth substance, and of their relation to the network, can be made out 

 clearly. The presence of firmly defined fibres or networks in that plane does 

 not interfere, from any point of view, with these appearances, since the former 

 lie embedded between the films, whether these are thick enough to seem smooth, 

 or thin enough to look blistered. Owing to the greater distinctness, optically, of 

 many striae or fibrils, it is necessary, where such are present to use great caution 

 in focussing for the film appearances. That is, such as belong to another plane 

 of network, for the greater refractiveness common to fibrillar structures may 

 optically interfere if they be above the focus. 



^ See Striation. 



* See Activities — filose. 



