416 APPENDIX II 



determine the points. The method may also be useful to others 

 studying other branches of immunity. As I have already stated, 

 my aim is to be able to assist in the diagnosis of infective disease 

 by this method, but a large amount of material will be required 

 before one can determine its value in this direction, and I have 

 mentioned its possibilities with reference to prognosis. The stage 

 in a disease in which measurable immunity appears in a leucocyte 

 also remains to be determined. 



To summarise the method by which I endeavour to assist in 

 a diagnosis in a case of infective disease, a small quantity of blood 

 from a patient is mixed with eight times its volume of the citrated 

 plasma of other persons who are known to be suffering from certain 

 infective diseases and also with the citrated plasma of a healthy 

 person. For this last purpose I sometimes use my own plasma. 

 The method has been described. The capillary tubes are kept 

 together in the revolving apparatus for about 14 hours. Then 

 some agar films are prepared from jelly which will excite move- 

 ments in living leucocytes, and samples of the contents of the tubes 

 are examined on these films. The number of living and dead cells 

 are averaged, and the difference between the lengths of the lives of 

 the cells when resting in healthy and infected plasmata are deter- 

 mined. When an infected plasma is found which will not com- 

 paratively shorten the lives of the patient's leucocytes, it seems 

 probable that the patient is suffering from the same disease as the 

 person from whom the plasma was taken. I generally confirm 

 this procedure by reversing the process and trying the patient's 

 plasma on the leucocytes of other persons suffering from the dis- 

 ease determined, taking care to make controls in this case as well 

 as in the first by making measurements with healthy plasma and 

 with the plasma of persons suffering from other diseases. 



The method described in this paper has two disadvantages: 

 first, in keeping the tubes at 30 C., and, secondly, in counting 

 500 leucocytes in each case, which is most tedious. The rest of 

 the method takes very little time; collecting the plasmata and 

 mixing them with the patient's corpuscles is soon accomplished, 

 and when the tubes are in the revolving apparatus they require no 

 further attention until the time has come to estimate the number 



