1909.] Modes of Division of Spirochseta recurrentis, etc. 503 



and & recurrentis that took from fourteen to sixteen minutes for complete 

 transverse division. 



The processes of transverse division, as seen in the larger S. anodontce, 

 exhibit yet further details. One of us (H. B. F.) has already shown that 

 Spirochetes move by («) an undulatory flexion of the body for forward 

 i progression, and (/?) a corkscrew motion of the body as a whole. It may be 

 of interest to note that in the transverse division of S. anodontce, as observed 

 in the living organism, reversal of the direction of the corkscrew or helicoid 

 motion of the parasite may occur. In a specimen about to divide trans- 

 versely, each of the halves vibrating about a node may reverse its direction 

 of torsional movement ; for example, a right-handed spiral may suddenly 

 become a left-handed one and vice versd. The resultant strain at the node 

 probably aids in the actual transverse division. 



Genercd Remarks. 



The fact that both longitudinal and transverse division take place explains 

 the occurrence of thick and thin and of long and short forms of the same 

 species of Spirochaete. Everyone who has worked on Spirochaetes is 

 cognisant of the occurrence of such polymorphism. 



Longitudinal division of S. recurrentis and S. duttoni, as before mentioned, 

 is best seen when the blood contains relatively few Spirochaetes — at the 

 beginning of infection and also at the end. Breinl (1907) noted the 

 occurrence of longitudinal division " especially at the time of the dis- 

 appearance of the parasites from the peripheral circulation." Numerous 

 long tenuous Spirochaetes are present in the blood during the height of the 

 infection, and these divide transversely. While allowing for the reactions of 

 the host upon the parasites, which reactions might induce the different forms 

 of division at different periods, it is also possible that the number of 

 Spirochaetes present in the blood at any given period may have some effect 

 on the direction of their division. The greater space necessary for 

 longitudinal division occurs at the onset of infection, when the Spirochaetes 

 are few. As the parasites grow in length and increase in numbers, it would 

 appear easier for transverse division to take place. 



We have, then, clearly shown that there is a distinct periodicity in the 

 direction of division exhibited by S. recurrentis and S. duttoni. Naturally 

 there is a time when both forms of division go on side by side. The 

 conflicting statements regarding the direction of division of Spirochaetes are 

 thus explained and reconciled. 



From the foregoing it is clear that the direction of division of Spirochaetes 

 cannot be used alone as a criterion of their protozoal or bacterial nature. 



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