APPENDIX II 407 



from a dead cell it also will become possible to measure the 

 lengths of the lives of leucocytes after they have been removed 

 from the body. And this will enable us to make comparative 

 measurements of the lives of leucocytes when they are mixed with 

 the plasmata of different persons. Supposing, therefore, it is true 

 that an infected plasma shortens the lives of a healthy person's 

 leucocytes but does not shorten the lives of the leucocytes of another 

 person suffering from the same disease, it may be useful to reverse 

 the process and assist in the diagnosis of infective disease by making 

 measurements of the lives of such a patient's leucocytes when they 

 are mixed with dfferent plasmata. For instance, if the leucocytes 

 of a person suffering from an indefinite infective disease are found 

 to be easily killed by the plasmata of persons suffering from a 

 variety of diseases, but are not comparatively easily killed by the 

 pasma of a person suffering from, say, typhoid fever, it might be 

 inferred that the patient is suffering from, or has recently suffered 

 from, typhoid fever, because his leucocytes are used to, or immune 

 against, that disease. 



The above is the enunciation of a problem which I set myself 

 to solve several years ago, and this paper describes the experiments 

 which have been conducted to investigate the last part of it i.e. 

 with the object of determining the actual measurements of the lives 

 of leucocytes when they are placed in the plasmata of people who 

 are suffering from various diseases. The earlier researches made 

 in order to differentiate living from dead leucocytes have already 

 been published in the Journal of Physiology (I), 1 and the actual 

 method employed to estimate how many living and how many 

 dead cells there may be in a given volume of citrated blood has been 

 described in The Lancet of January 16, 1909 (2). This method 

 may be again briefly summarised thus: 



Method for counting the number of living and dead leucocytes in 

 a given sample of citrated blood. The following solutions are pre- 

 pared and a jelly is made from them. 1. A volume of Unna's 

 polychrome methylene blue (Grubler) is diluted with two volumes 

 of water. 2. A solution containing 2 per cent of agar in water, 



1 The figures within parentheses refer to the bibliography at the end of the 

 article. 



