64 MECHANISM OF DISINFECTION AND HEMOLYSIS 



fragile cells are laked almost immediately, the resistant ones survive 

 for many hours, but most of the cells succumb during an intermediate 

 period when the observed rate of hemolysis is at a maximum. 

 When hemoglobin finally begins to diffuse from a given erythrocyte, 

 the process is so quickly completed that it may ordinarily be regarded 

 as instantaneous. It is obvious that an increase in the relative 

 number of, for example, the more fragile cells would accelerate the 

 earlier stages of hemoglobin liberation, while a decrease would produce 

 a corresponding retardation. 



II. 



There are two ways of expressing graphically the progress of hemol- 

 ysis: the time curve or course, whose ordinates are proportional to 

 the total number of cells laked; and the rate curve, whose ordinates 

 are proportional to the number of individuals laking in a unit of time. 

 The former is the more frequently found in hemolytic studies, while 

 the latter is the "mortality curve" of vital statistics. If one of these 

 curves is known the other may be found by graphical methods. For 

 instance, let us suppose that we have only the mortality curve: the 

 ordinates of the time curve represent the total number of individuals 

 having insufhcient resistance to survive beyond the indicated time; 

 the area enclosed by the mortality curve corresponds to the total 

 number of individuals ; the area enclosed by the ordinate at any point 

 on the X axis and the part of the mortality curve to the left of the 

 ordinate, is proportional to the number of cells having less than the 

 indicated resistance, and is therefore also proportional to the corre- 

 sponding ordinate of the time curve. If the mortality curve is plotted 

 on suitable coordinate paper these areas may easily be estimated with 

 sufficient accuracy, ordinates proportional to them erected at the 

 corresponding points on the x axis, and their tops connected by a 

 smoothed curve. This will be the time curve, and, since the process of 

 finding it is a process of integration, it is at the same time an integral 

 curve. 



If we have only the time curve, or integral, it is easy to see that the 

 rate of hemolysis, that is the number of cells laking in a unit of time, 

 is represented by the slope of the time curve; the steeper the time 



