104 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



the only fallacies likely to arise are from the use of unsuitable 

 materials, especially the antigen, a fallacy which, of course, may 

 occur whatever method is used. Another advantage is that it is 

 possible to perform a rapid quantitative estimation, by determining 

 the highest dilution of antigen which will just give a positive 

 reaction. We will suppose that there is no haemolysis with 

 antigen diluted i in lo. Prepare a second antigen, diluting it 

 I in 30, and repeat the test. If there is still no haemolysis, try at 

 I in 50, and, if necessary, higher. I regard a reaction at 1 in 10 as 

 definite but weak, one at i in 30 as moderate, and one at i in 50, 

 or over, as strong. I have seen a serum which reacted positively 

 with antigen diluted over 300 times. There are other methods of 

 performing a quantitative test, but this is the simplest. A series 

 of quantitative estimations is of enormous value, as it enables us 

 to gauge the effect of treatment. 



Second Modification of the Test. 



Good anti-human amboceptor is not at present easily obtained, 

 and for the benefit of those who may be able to get sheep's 

 corpuscles I may point out that the process described above can 

 be carried out in exactly the same way, using washed sheep 

 corpuscles and anti-sheep serum, which is an ordinary article 

 of commerce. The process is exactly the same, but a word or 

 two is necessary as to the materials. The sheep's blood must be 

 obtained fresh from the slaughter-house. The best method is to 

 prepare a flask containing a few glass beads or fragments of glass 

 tubing, plugging it with cotton-wool, and sterilizing by hot air.- 

 The butcher is to be instructed to receive the blood into this 

 flask, and to rotate the latter gently for a few minutes. It will 

 then be defibrinated, and will no longer clot. When received in 

 the laboratory, a few cubic centimetres are to be washed in sterile 

 normal saline solution three times, centrifugalizing down each 

 time. Washed corpuscles will keep about a week in sterile 

 normal saline solution to 300 parts of which i part of formalin 

 has been added. 



The anti-sheep serum must be diluted before use, as it is 

 usually too strong when sent out. The degree of dilution varies 

 greatly ; I have had samples which have been quite inert and 

 others that have acted when diluted 1,200 times, and, as a rule it 

 works well at a dilution of i in 500 or 600. The method to be 



