STRUCTURE OF THE CELL CONTENTS 33 



unconditionally applicable, as the following example will show. A one per cent, 

 solution of common salt produced no plasmolysis in Clostridium buttjricum when 

 the cultures were only two days old, and the cells consequently young ; whereas 

 after a further four days they were, without exception, completely plasmolysed. 

 It will perhaps be useful to recall that a solution of 0.5 gram of NaCl in 100 

 grams of water is usually known as physiological salt solution, and is frequently 

 used under the supposition that it neither takes up nor gives up water from or 

 to the cells, an assumption that, in view of the preceding figures, cannot be 

 universally justifiable. 



If it is desired to render permanent ("fix") the plasmolytic condition of the 

 cells, they must be killed, a result easily obtained by the use of sublimate or 

 iodine solution. Ten per cent, lactic acid is also an excellent fixing medium, 

 instantaneous in action. After fixing, staining can be effected. More detailed 

 information on the practice of fixing will be found in a work by A. ZIMMER- 



MANN (I.). 



35. Structure of the Cell Contents. 



This study, which presents no small difficulty on account of the minuteness 

 of the organisms to be examined, has been closely followed up during the past 

 several years only. All that was previously known was 

 that the cell contents of the bacteria consisted of a 

 homogeneous invacuolate plasma, in which small, highly 

 lustrous granules were frequently seen embedded. 



BUTSCHLI (I.) in 1889 discovered in a few large 

 chromogenic bacteria (e.g. Chromatium Okenii and 

 phidomonas jenensis), as also in /Spirochcete serpens 

 and Beygiatoa, that their cell contents could, as a rule, 

 be distinguishable into two parts, viz., a central body 

 and a parietal layer, the latter being adjacent to and 

 surrounded by the cell wall. 



The parietal layer may either surround the central 

 body on all sides, so that the latter nowhere touches 

 the cell wall, or may be restricted to one side only, in 

 which event it is generally, in the case of rod-shaped 

 bacteria, found at the two poles. This differentiation 

 of the cell contents can be rendered visible (Fig. 9) 

 by suitable stains, e.g. haematoxylin, which is most 

 readily taken up by the central body, thereby render- 

 ing it easily distinguishable from the more slightly 

 coloured parietal layer. 



This treatment brings out a second and much 

 more important fact : the central body appears as a 

 complicated structure, reminding one of that seen in 

 honeycomb. A number of granules of red-violet 

 colour called by Biitschli " red grains" are stored 

 in a reticular framework which is coloured blue by the 

 staining dye. These granules do not occur in every 

 cell, and no cell has more than one. These enclosures 

 are detectable, even in the unstained preparation, on 

 account of their high refractive power. They the bodies, not their enveloping 

 framework were first observed by V. BABES (I.), then studied by P. ERNST 

 (I. and II.), and were regarded as the starting-point of spore formation, being 

 on that account designated sporogenic granules ; but this assumption has with 

 good reason, been contested by later workers. For a more accurate examination 

 i C 



FIG. 9. Cliromatium Okeuii. 



A. Longitudinal section. 



B. Cross section. 



First killed, then freed from 

 bacterio-purpurin and sul- 

 phur granules by solvents, 

 and finally stained with hae- 

 rnatoxylin. The reticulated 

 structure of the (hatched) 

 central body (c), as also of 

 the parietal layer (b), and tlie 

 dark chromatin granules (s), 

 Biitschli's "red grains," can 

 then be detected. Magn. 

 2000-2500. (After Biitxchli.) 



