34 BACTERIOLOGY. 



Monas (Spumelld) vulgaris and in Chro- 

 muhna. 



Aided by the foregoing facts, we may attempt 

 to advance beyond Conn's " form-genera " and 

 " form-species " of bacteria to a conception of 

 natural genera and species. According to 

 Hueppe and De Bary, the endosporous bacteria 

 must be fundamentally separated from the ar- 

 throsporous. For the sake of clearness, let us 

 cite some examples. The specific disease 

 germs found in anthrax, typhoid fever, diph- 

 theria and tuberculosis have the form of rods 

 and are consequently known in medical liter- 

 ature as Bacilli. But the anthrax rods, in 

 the light of their whole life history, belong to 

 a species that forms filaments and produces 

 endospores of a well-known and characteristic 

 kind ; the bacteria of typhoid fever and of 

 diphtheria form no endospores, and the tubercle 

 rods probably form chlamydospores. Accord- 

 ing to Cohn's earlier view the genera Bacillus 

 and Bacterium were to be distinguished only 

 by the length of the rods, but according to his 

 later conception the difference lies not in the 

 dimensions of the rods, but in the fact that 

 the one forms endospores while the other does 

 not. In accord with this terminology, there- 

 fore, the anthrax rods belong to the genus 

 Bacillus, the typhoid and diphtheria rods to 



