SURFACE S T K U C T U U i: S 35 



and Sraccy, 1943 ; Henry, Staccy and Tcccc, 1945). According to these 

 authorities it is the dit^erence in prc^portion of ribose and deoxyribose nucleic 

 acids which determines the Gram-reaction, the former being preponderant 

 in Gram-positive bacteria. On the other hand Mitchell and Moyle (1950) 

 attribute Gram-positivity to the presence ot a phosphoric ester, the occurrence 

 of which is independent of the concentration of ribose nucleic acid. Hoftman 

 (195 1 ) suggests that a difference in the tyrosine content of the pentose nucleo- 

 proteins ot Gram-positive and Gram-negative bacteria might account for 

 the difterence. 



As in other types oi cell, the cell membrane contains an element which 

 stains with lipid-soluble dyes, and there is little reason to doubt that it is 

 similar in most respects to the cell membranes which are, perhaps, the most 

 important organs of any living cell, and which serve to insulate the cell 

 contents from the effects of variation in the outside medium by the exercise 

 oi a regulatory function upon the passage of dissolved material through their 

 surtace. 



The actual demonstration ot the cell-membrane as a separate structure has 

 been achieved in lysozyme digested bacteria by Weibull {1953 b,c) and Tomcsik 

 and Guex-Holzer (1954) . In the last stages of dissolution, the protoplasts appeared 

 as " ghosts," and the empty membrane survived momentarily. The behaviour 

 of the cell membrane at cell division provides additional evidence that it is a 

 positive structure, and not merely an altered surface or interface. The septa 

 which initiate cell division are clearly resoluble, although surrounded on both 

 sides by cytoplasm. 



The large quantity of nucleic acids contained in, or associated with the 

 cell membrane may be a cause ot contusion. It is observed that, as in the case 

 ot plant cells, the effect ot certain cytological procedures, for example formalin 

 fixation or acid-hydrolysis, may be to increase the basophilia of the nucleus 



Fig. 12 



ELECTRON MICROSCOPY OF CELL ENVELOPE MATERL\L 



Spirillum sp., wall of crushed cell. The outer layer is represented by the striated pattern 



in the upper part of the plate, the inner by the pattern of regular globules below, .\lthough 



not conclusive in itself, this appearance is in accordance with the view that the envelope 



