8 MICROBES AND TOXINS 



much less altered than the structures which surround them : 

 therefore it is supposed that they must have survived tissues 

 which they destroyed. 



The presence of bacteria in coals derived from organic 

 matter should not astonish us. But it appears difficult to 

 believe that bacteria have been the only agents in the formation 

 of coal. The study of their form is extremely difficult ; fine 

 particles of iron pyrites and little crystals often imitate bacterial 

 forms in the thin sections of coal, so difficult to prepare and 

 examine by transmitted light under the microscope. On the 

 other hand the fermentation of cellulose does not explain the 

 frequent impregnation of the debris by a blackish, bituminous 

 material, nor perhaps does it really explain the enrichment in 

 carbon of the deposits ; further, there have been produced from 

 the fermentation of fatty bodies, resins and similar volatile 

 substances, phenol bodies like those found in coal (E. Duclaux). 

 There is nothing surprising in the presence of algae in the 

 Bogheads^ for these are precisely the coals derived from algae 

 and often named algal coals. Their formation was due to 

 luxuriant algae growths rapidly developed on the surface of 

 stagnant pools, which then sank to the bottom carried down 

 by a coagulum in the peaty water ; this mass contained 

 bituminous substanceswhich must have come from elsewhere, for 

 there is no indication that they took their origin on the spot by 

 an alteration of the algae. It is these bitumens which have 

 produced the carbon enrichment of the mass, so that on the 

 whole instead of destruction a preservation process has taken 

 place. In other cases, instead of this enormous growth of 

 algae, clouds of pollen and spores from the primeval forests 

 have been deposited : these " rains of sulphur " also sank in 

 the peaty water and became saturated with bitumen, hence 

 the so-called spore and pollen coals. 



We ought not to be too ready to reject the bacterial theories 

 of the formation of the various coals, especially should it turn 

 out to be impossible to explain without microbes the formation 

 of the bitumen which impregnates them. The small lower 

 algae are rich in fats and capable of yielding petroleum bodies 



