424 SPIRILLUM CHOLERA ASIATICS. 



screw-like twisted threads, and therefore in their simplest 

 form may be looked on as fragments of spirilla. The 

 average length of the individual curved bacillus is about 

 1*5 p.., varying between *8 ft. and 2 ^. ; the average 

 thickness is from ^ to i of the length. The youngest 

 individuals either show a very slight curve or no curve 

 at all ; the more fully formed ones generally show in 

 fresh unstained specimens a distinct curve, sometimes 

 only a slight bend, sometimes a full half circle ; in the 

 dried and stained specimens a larger number show a 

 less curve or are even straight, the difference being due 

 to the method of preparation. After division the two- 

 individuals often remain united together, and thus, 



Fig. 116. (After Koch.) Cover glass preparation 

 from the border of a drop of meat infusion con- 

 taining a pure cultivation of the comma bacilli. 

 Long screw-like threads () X 600. 



according to the age and degree of development, they 

 form short and slight, or longer and more markedly 

 bent and S-shaped figures ; when examined in drop cul- 

 tivations it may be seen that the two component parts 

 of the " S " do not lie in one plane, but represent the 

 commencement of a screw. As the result of the pre- 

 paration we not uncommonly find in stained preparations 

 e- shaped forms ; it is probable that in this case the 

 rods have become bent and displaced in the middle, so 

 that the concavities, which were originally opposed to 

 Spirilla. eacn other, now look in the same direction. In drop 

 cultivations there is almost always a formation of long 

 screw-like threads or true spirilla, which may consist of 

 10, 20, or 30 narrow turns; this continued adhesion of 

 the newly developed individuals, to which the spirilla 



