THE CELL 



45 



.4 



these elements bear to one another and to the cell as a whole have 

 been the su])ject of much investigation and si:)eculali()n. Tin- earlier 

 cytologists concerned themselves with 



the question as to whether ])rot()i)lasin f" ~~ • — . 



was homogeneous {i.e., a mere solution 

 or at most a mixture of various sub- 

 stances) or had a definite structure. 

 The theory of a structureless proto- 

 plasm having been long since aban- 

 doned, the question as to the character 

 of the protoplasmic structure still re- 

 mains unanswered. 



Altmann's granule theory considers proto- 

 plasm as composed of fine granules embedded 

 in a gelatinous intergranular substance. 

 Altmann believed these granules the ultimate 

 vital elements, and for this reason gave them 

 the name of bioblasts (Fig. 2, b). 



According to Butschli, protoplasm is a 

 foam or emulsion, the microscopic appearance 

 of which can be simulated by artificial emul- 

 sions. He ascribes the appearance of a rcti('- 

 ulum to the fact that each little foam space 

 forms a complete cavity filled with fluid, the 

 cut walls of these spaces giving a reticular ap- 

 pearance on section (Fig. 2, c and Fig. 3). 



Other investigators consider protoplasm as 

 made up of (i) a fibrillar element, either in the 

 form of a network of anastomosing fibrils 

 (cytoreticulum) or of a feltwork of indepen- 

 dent fibrils (filar mass or miton), and (2) a 

 fluid or semi-fluid substance which fills in the 

 meshes of the reticulum or separates the fibrils 

 (interfilar mass or paramiton) (Fig. 2, o). 



That the question as to the ultimate struc- 

 ture of protoplasm stiU remains unanswered is uZ'''J'~r^^^f °' emulsion struc- 

 *^ ^ tare ot protoplasm accordmg to 



dependent mainly upon the extreme technical Butschli (Biitschli). A, Epidermal 

 difficulties which have confronted the cytolo- ^?^ of ^he earthworm. B, Peri- 

 „• , T • • * 1 I, u pneral cytoplasm of sea urchin's 



gist. Livmg protoplasm has a homogeneous egg. C, Artificial emulsion of oUve 

 glossy appearance, showing even under the oil, sodium chlorid and water, 

 highest magnification rarely more than a 



granular structure. It is usually only after death of the cell and the use of 

 chemical fixatives and stains, that the so-called "structure" of protoplasm 

 becomes visible. How closely the picture presented by such chemically treated 

 protoplasm corresponds to the structure of living protoplasm is as yet unde- 





