THE CHOLERA VIBRIO 121 



distance between their tips (LJ . The proportion between the difference 



of these two values and the true length of the cells ^~ ^' serves 



as an abstract measure of the variation in curvature. The mecin 

 values of this index of curvature are presented in Table XXV. 

 It will be seen that with the initiation of growth at six hours this 

 value began to increase, reaching its maximum at twelve hours, ap- 

 proximately at the end of growth, and then progressively decreasing 

 again to a minimum at the end of the period of observation, at 

 ten days. That the degree of curvature is correlated with the rate 

 of growth is quite apparent by an inspection of Plate 2. Particularly 

 during the first twenty-four hours the curve for index of curvature 

 is practically parallel with the growth curve. The maximum is main- 

 tained during the resting phase. Since the cells increase in curva- 

 ture as they decrease in area-length index, that is as they become 

 more slender, it seems probable that there would be found a cor- 

 relation between the degree of slenderness and the degree of curva- 

 ture, and this seems all the more apparent in the composite photo- 

 graphs given in Plate 2. When, however, the index of curvature 

 was plotted against the area-length index with cells from the nine 

 hour, eighteen hour, and thirty-six hour samples, no such correla- 

 tion could be established. That is, while the period of greatest 

 curvature corresponds with the period of greatest slenderness of 

 the cells, it is not necessarily the most slender cells which are the 

 most curved. 



The frequency distribution of the cells with regard to their 

 area-length indices is presented in Plate 2, where an attempt has 

 been made to show in one illustration nearly all the morphologic 

 variations of this organism. The frequency distribution curves have 

 been erected in succession behind each other in isometric perspec- 

 tive. On the upper face of the parallelopiped containing them the 

 mean area-length index has _^ been plotted. On the right face the 

 rate of growth is shown by plotting the logarithms of the number 

 of cells. On this face there is also given the mean index of curva- 

 ture. The significance of the area-length index is indicated in the 

 small figure at the bottom of the plate, which presents composite 

 photographs of all of the cells from the five-hour sample arranged 



