40 Transactions. — Miscellaneous. 



in the bodies of men and animals, and of their relation to 

 disease and its cure. 



The word " bacterium," the latinised form of jBaKTiqpiov, and 

 meaning a staff, refers to the appearance under the microscope 

 of one division of micro-organisms, from \Yhich the name has 

 been distributed to designate these small beings in general. 

 The term "microbe," used by the French, indicates a small 

 living thing. They have been alternately classed as animals 

 and as plants. Ehrenberg, in his work on infusion-animalcules, 

 published in 1838, described them as animal forms, their power 

 of movement, as he says expressly, leading him to place them 

 in the animal kingdom. Under the microscope some forms 

 are seen to dart across the field with very rapid movements ; 

 others have spiral, corkscrew, or vacillating or undulatory 

 motion. Cocci have molecular or " Brownian " movements. 

 Many kinds of bacteria are motionless. The exact place of 

 bacteria in a biological classification may be held to be still 

 undetermined. They have been placed among the fungi, 

 inasmuch as bacteria consist of vegetable cells destitute of 

 chlorophyll, and they have other characteristics of fungi. 

 Other observers consider them as algae, from the fact that 

 some species do contain chlorophyll. Looking on them as 

 plant-forms, perhaps the safest classification is that which 

 refers them to the Thallophyta, in which Sachs places them. 

 Other biologists place them in a separate order, which they 

 term the Protista, to be considered as between the animal and 

 vegetable kingdoms. At the same time, as de Bary says, " it 

 is merely a matter of convention in the case of these simple 

 organisms where and how we shall draw the line between tlie 

 vegetable and animal kingdoms." 



Bacteria consist of cells which are, so far as is known, 

 destitute of nuclei. In form the cells are globular or ovoid, 

 or elongated as cylindrical or spindle-shaped rods. The 

 globular and rod-shaped forms have mostly a diameter of 

 •001 of a millimetre, or about o5-jooin. The length of the 

 rods is from two to four times the transverse diameter. 

 Chemically the cells are composed of protein or mycoprotein, 

 and have a distinct cell-wall, which possesses distinct physical 

 and chemical properties from those of the cell-contents. 



Various classifications have been made. The classification 

 of bacteria hitherto most commonly followed is that of Cohn, 

 who takes the form of the bacteria as the basis. He gives 

 four classes: 1, Spherobacteria, globular; 2, Microbacteria, 

 short rods ; 3, Desmobacteria, long rods ; 4, Spirobacteria, 

 spirals. 



This brings us to the terms used in describing bacteria. 

 The globular cells are called cocci, from kokk-os, a berry, and 

 from which, again, we have micrococcus and macrococcus. 



