296 PHENOMENA OF PUTKEFACTION. 



locomotive activity, and in fact this power is possessed by the 

 various species of Proteus in a high degree, manifesting itself both 

 by a rapid forward movement and a concurrent (longitudinal) axial 

 rotation. Hence, the coupled cells describe a kind of double cone, 

 the vertex of which is at their point of junction. In addition to 

 the above-named forms, gelatin cultures also yield spirilla, with two 

 to four convolutions ; thread-cells, which may grow to a length of 

 100 ft; and finally " spirulina," or threads bent in the form of a 

 bow, with ends twisted into a queue. Under special circumstances 

 involution forms are also produced : the cells swell up in the shape 

 of a pear, and resemble spermatozoa, dumb-bells, &c., in form. 



Proteus mirdbilis exhibits a very decided tendency for pro- 

 ducing such involution forms. Globular or pear-shaped forms, 

 3-7 ju, in diameter, are very frequently developed in the cultures 

 of this microbe, which also exhibits polymorphism in a high degree, 

 and in this particular greatly resembles the preceding species. 

 Here also we meet with short rods, long rods, spirilla, and thread- 

 cells, rapidly moving one through another in varied alternation. 

 At the same time small but unmistakable differences exist. Thus, 

 for example, these threads not unfrequently attain a length of 200 /x, 

 i.e. double the maximum size of the first-named species. 



Proteus Zenkeri differs from the two preceding species mainly 

 in its inability to liquefy gelatin, but resembles them in other 

 particulars, though its cells are generally smaller, the least of them 

 being globular in form and 0.4 /x in diameter. Short rods (0.8 //, 

 long) joined in pairs are frequently encountered. These three 

 species are unique in the bacterial kingdom in point of motile 

 power, which they possess to such a high degree that a solid 

 medium containing only 5 per cent, of gelatin is unable to restrain 

 them, and they make their way across it in all directions. In order 

 to stop this roving motion the gelatin content must be increased to 

 10 per cent. This peculiarity is not only of physiological interest, 

 but is also decidedly important so far as practical bacteriology is 

 concerned, in that it indicates the futility of employing nutrient 

 gelatin media containing less than 10 per cent, of gelatin for the 

 preparation of pure plate cultures of Proteus species. To complete 

 the characterisation of these three species, it should be mentioned 

 that none of them forms endospores, and that their growth may be 

 arrested by depriving them of oxygen, though they do not neces- 

 sarily die in consequence. They will not thrive in mineral nutrient 

 media, such as those of Cohn and N"ageli. When grown in albu- 

 minous media, they produce stinking decomposition. A. BRODMEIER 

 (I.) proved that in neutral or alkaline solutions Proteus vnlgaris is 

 able to convert urea into ammonium carbonate. He thus refuted 

 the assertions of Leube to the contrary, and confirmed the discovery 

 of Schnitzler and Hofmeister. 



No pretension can be made in the present work of giving a 

 complete description of all known forms of putrefactive bacteria, 



