CHEMICAL COMPOSITION OF BACTERIA. 13 



Among the bacteria Biitschli further finds confirmation of his views on 

 the mesh-like structure of protoplasm generally. A bacillus, he finds, 

 consists of four or five more or less square meshes laid end to end, 

 and he gives microphotographs of bacilli presenting such appearances 

 (vide Fig. i, Nos. 150 and b}. With regard to these observations 

 of Biitschli, Fischer holds that the appearances seen were due to 

 plasmolysis, and considers that there is no evidence of differentiation 

 between protoplasm and nucleus in the bacterial cell. 



The Chemical Composition of Bacteria. In the bodies 

 of bacteria many definite substances occur. Some bacteria 

 have been described as containing chlorophyll, but these are 

 properly to be classed with the schizophyceae. Sulphur is 

 found in some of the higher forms, and starch granules are 

 also described as occurring. Many species of bacteria, 

 when growing in masses, are brilliantly coloured. Com- 

 paratively few bacteria, however, associated with the pro- 

 duction of disease give rise to pigments. In some of the 

 organisms classed as bacteria a pigment named bacterio- 

 purpurin has been observed in the protoplasm, and similar 

 intracellular pigments probably occur in some of the larger 

 forms of the lower bacteria and may occur in the smaller. 

 Exact observation is, however, a work of great difficulty, and 

 in the majority of the smaller forms it is impossible to 

 determine whether the pigment occurs inside or outside 

 the protoplasm. In many cases, for the free production 

 of pigment abundant oxygen supply is necessary. On the 

 other hand, sometimes, as in the case of spirillum rubrum, 

 the pigment is best formed in the absence of oxygen. 

 Sometimes the faculty of forming it may be lost by an 

 organism for a time, if not permanently, by the conditions 

 of its growth being altered. Thus, for example, if the B. 

 pyocyaneus be exposed to the temperature of 42 C. for 

 a certain time, it loses its power of producing its bluish 

 pigment. Pigments formed by bacteria often diffuse out 

 into, and colour, the medium for a considerable distance 

 around. 



Comparatively little is known of the nature of bacterial pigments. 

 Zopf, who has devoted much attention to the pigments occurring in the 



