10 BACTERIOLOGY 



of space, forming chains when the individuals remain adherent or 

 single individuals when they become separated. In others, as in 

 certain Coccaceas, division may take place first in one direction, 

 forming two adherent hemispheres, as in the gonococci, followed 

 by a subsequent division of the two hemispheres in a direction at 

 right angles to the first, resulting in groups of four, tetracocci, 

 or in larger quadrangular plates as in Merismopedia. In Sarcina 

 division takes place at right angles to one another, forming 

 cubical packets, as in Fig. 4, w. In the Bacteriaceas proper the 

 organisms are unicellular and unbranched. The union of indi- 

 viduals into groups, chains, or zoogloea, even when there is appa- 

 rent branching, as in Fig. 2, G, offers no morphologic difficulties, 

 inasmuch as each individual in the group is biologically distinct. 

 In the Mycobacteriaceae the cellular protoplasm, on the other 

 hand, may show true dichotomous branching, as seen in tubercle, 

 diphtheria, and in influenza bacilli (see Fig. 3, c, d, e, f). Here 

 again the branching is quite distinct from the false branching 

 of Cladothrix, inasmuch as in the former the protoplasm in the 

 body and in its branches is continuous, while in Cladothrix, 

 Fig. 3, a, this continuity is absent. On the contrary, we have a 

 chain of individuals, one of which is thrust to one side and out 

 of line with the others, and which continues to elongate and 

 divide in the new direction, thus producing a false branching. 

 Furthermore, in the Mycobacteriaceas the individual organisms, 

 whether simple, either rods or filaments, or branched, are con- 

 tinuous or unicellular. In the vegetating body of the true 

 fungi, which are most closely aUied to the Mycobacteriaceae, 

 while there is the same character of branching, the filaments 

 are longer and generally divided by septse. The higher Lepto- 

 thrix and the lowest Hypomycetes are, however, so closely 

 related that it is difficult to draw a hard and sharp line be- 

 tween the two groups. 



