10 GENERAL MORPHOLOGY AND BIOLOGY 



are brilliantly coloured, though few bacteria associated with the 

 production 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 ; but it is usually 

 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; but 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, however, has found that many of them belong to a group of 

 colouring matters which occur widely in the vegetable and animal 

 kingdoms, viz. the lipochromes. These lipochromes, which get their 

 name from the colouring matter of animal fat, include the colouring 

 matter in the petals of Ranunculacege, the yellow pigments of serum and 

 of the yolks of eggs, and many bacterial pigments. The lipochromes are 

 characterised by their solubility in chloroform, alcohol, ether, and 

 petroleum, and by their giving indigo-blue crystals with strong sulphuric 

 acid, and a green colour with iodine dissolved in potassium iodide. 

 Though crystalline compounds of these have been obtained, their 

 chemical constitution is entirely unknown and even their percentage 

 composition is disputed. 



Some observations have been made on the chemical structure 

 of bacterial protoplasm. Nencki isolated from the bodies of 

 certain putrefactive bacteria proteid bodies which, according to 

 Ruppel, appear to have been allied to peptone, and which 

 differed from nucleo- proteids in not containing 'phosphorus, 

 but many of the proteids isolated by other chemists have 

 been allied in their nature to the protoplasm of the nuclei 

 of cells. Buchner in certain researches obtained bodies of this 

 nature allied to the vegetable caseins, and he adduces evidence 

 to show that it is to these that the characteristic staining 

 properties are due. Various observers have isolated similar 

 phosphorus-containing proteids from different bacteria. Besides 

 proteids, however, substances of a different nature have been 

 isolated. Thus cellulose, fatty material, chitin, wax-like bodies, 

 and other substances have been observed. There are also found 



