VACUOLES 27 



4. Those who consider the bacterial protoplasm to con- 

 sist of a central endoplasm throughout which the nuclein 

 is diffused and an external layer of ectoplasm next to the 

 cell wall, (Biitschli, Zettnow). 



5. Those who say that the bacterial cell contains a dis- 

 tinct nucleus, at least in most instances. These authors 

 base their claims on staining with a Giemsa stain (Feinberg, 

 Ziemann, Neuvel, Dobell, Douglass and Distaso). 



That nucleoproteins are present in the bacterial cell in 

 relatively large amounts is well established. Also, that 

 there are other proteins and that the protoplasm is not all 

 nuclein. 



Some workers, as noted above, have been able to demon- 

 strate collections of nuclein by staining, especially in very 

 young cells. In older cells this material is in most instances 

 diffused throughout the protoplasm and cannot be so dif- 

 ferentiated. 



The following statement probably represents the generally 

 accepted view at the present time : 



A nucleus as such is not present in bacterial cells except 

 in a few large rare forms and in very young cells. Nuclein, 

 the characteristic chemical substance in nuclei, which when 

 aggregated forms the nucleus, is scattered throughout 

 the cell contents and thus intimately mingled with the 

 protoplasm, and cannot be differentiated by staining as in 

 most cells. 



The close association of nuclein and cytoplasm may explain 

 the rapid rate of division of bacteria (Chapter VIII, page 72) . 



The chemical composition of the bacterial cell is discussed 

 in Chapter VII. 



In addition to the essential parts just described the bac- 

 terial cell may show some of the following accidental struc- 

 tures: vacuoles, cay sides, metachromatic granules, flagella, 

 spores. 



Vacuoles.— Vacuoles appear as clear spaces in the cyto- 

 plasm when the organism is examined in the living condition 

 or when stained very slightly (Fig. 19). During life these 

 are filled with liquid or gaseous material which is sometimes 

 waste, sometimes reserve food, sometimes digestive fluids. 



