Abstract
The time-dilution curve obtained for most haemolytic systems, which is described by the equation
can be analyzed by a method already described (Ponder and Yeager 1 ). The method is somewhat laborious and the analysis is more easily carried out as follows:
One requires a piece of cellophane, about 40 cm. square. The length of the right hand side is divided in such a way that the divisions represent 12.2, 24.4, 36.6, 48.8, 61.0, 73.2, 85.4, and 100% of that side. A series of lines are drawn on the cellophane joining each of these divisions to the left hand corner.
The time-dilution curve is drawn on a large scale in the usual way, and the asymptote (x) is marked with a horizontal line. Place the lower edge of the cellophane along the abscissa of the curve, and move it from right to left until the oblique line corresponding to the 100% division passes through the point at which the horizontal line corresponding to the asymptote cuts the ordinate of the curve. The oblique lines then cut the ordinate of the curve at a series of points. From the curve, read off the time corresponding to each of these points, add up the times, and divide by the time corresponding to the oblique line for 85.4%. Call the result S. The value of n(= 1/p) is found by consulting Table I.
In this way a time-dilution curve can be analyzed in less than a minute, and, if the curve is of the usual form, the value of n is obtained with an error no greater than ±0.05, for values not shown in the table can be found by interpolation. When large numbers of time-dilution curves are obtained in the course of an investigation, a rapid method of analysis is a great convenience, although it is often necessary to analyze the curves more carefully later on.
Get full access to this article
View all access options for this article.