ON THE BACTERIA. 147 



III. — Bacilli are slender filaments, straight, sometimes of con- 

 siderable length, varying from i-6,oooth to 1-2, 500th of an inch 

 in length, endowed or not with motion ; and, under cultivation, 

 forming spores, which lie in rows within the rods, and which at 

 length fall to pieces, liberating the germs. 



IV. — Vibriones are slender filaments, always undulating, dis- 

 tinguished from Bacteria by their wavy, serpentine movements. 



V. — Spirilla. The largest of all the Bacteria, (from 1-1,5 00th 

 to 1-2, 000th of an inch long) are characterised by the spiral 

 coiling of the cell, and by their cork-screw-like movement. 



Such being a slight sketch of the morphology of the Bacteria, 

 we now come to consider what is the part played by them in the 

 processes of putrefaction and of disease. 



Putrefaction, as we know, is the tendency of all dead organic 

 matter, under certain conditions, to undergo various processes of 

 disintegration, evolving offensive gases, and giving rise to various 

 new chemical combinations. Intimately connected with this pro- 

 cess is found to occur the growth and multiplication of living 

 organisms. The point we have first to consider is — How they 

 come there. This question has been for many years the battle- 

 field of the various theories of the Origin of life. Here the 

 biologists are ranged into two opposing factions. On the one side 

 are placed those, who, carrying the doctrine of Evolution to its 

 fullest extent, suppose that the unbroken chain of continuity which 

 runs through the whole organic world — plant and animal gliding 

 imperceptibly into each other — is also carried downwards into the 

 inorganic — the living gradually gliding into the non-living — until 

 all Nature is one grand sequence and continuous whole. The 

 link between the organic and the inorganic being the Bacteria ; 

 and the mode of their development being that they are the result 

 of the normal re-action of the air, under certain circumstances, 

 upon the non-living elements with which it is in relation. The 

 process being analagous to the phenomenon of crystallisation ; as 

 in the formation of crystals, certain molecules, under certain 

 conditions, assume definite geometrical forms, so certain other 

 molecules under certain other conditions, assume the appear- 

 ance and attributes of vitality. 



On the other side are those biologists who say that though 



