SPIROCH^TES : MOVEMENTS 71 



to be a periodicity in the direction of division ex- 

 hibited by them. Longitudinal division is the 

 commoner method of multiplication when the infec- 

 tion is scanty, and this is succeeded by transverse 

 division when the parasites are very numerous in 

 the blood. Naturally, there is a bridging period 

 when the two forms of division go on side by side, 

 but it has been shown to be a somewhat short one. 



The movements of spirochsetes are of extraordinary 

 interest, not only for their own sake, but also on 

 account of the numerous inaccuracies that have 

 arisen owing to normal movements of growing 

 individuals being mistaken for stages in division. 

 Again, some persons have denied the existence of 

 longitudinal division because they themselves have 

 not observed it. Needless to say, their misfortune 

 does not invalidate the fact of undoubted longi- 

 tudinal division. It merely emphasizes the need of 

 more careful and prolonged observation, together 

 with a search for the probable periodicity. 



Movements in spirochaetes depend partly on the 

 body, but chiefly on the myonemes of the mem- 

 brane. Their forward movements have been carefully 

 analysed, and two components occur. The first 

 movement is a wave-like (vibratory) motion of bend- 

 ing or flexion of the body which is mainly for 

 progress in a forward direction. This movement is 

 accompanied by a second, that of a spiral or cork- 

 screw-like motion of the body as a whole, due to the 

 spiral winding of the membrane. 



Spirochaetes can reverse their direction of progress 

 with the greatest of ease. They pass and repass the 



