160 APPLIED IMMUNOLOGY 



ticularly the difficulty of sending serum for a distance 

 that is absolutely haemoglobin- free, the advertisements 

 of commercial laboratories that they are prepared to 

 carry it out as a diagnostic measure are premature. 



The optical or polariscopic method of reading the 

 reaction, for which a polariscope is necessarj^ gives 

 practically the same results as the dialysis-ninhydrin 

 method, but at present entails so much expense that it 

 is out of the reach of the ordinary laboratory. 



Abderhalden and others are at present working on 

 similar protein-splitting reactions for the diagnosis of 

 cancer and other diseases, which promise much for the 

 future. 



Pearce and Williams have worked out a technic 

 which promises to do away with many of the serious 

 difficulties of the test, by which the reaction can be 

 carried on in ordinary test-tubes instead of the dif- 

 fusion shells. The mixture of serum and placenta is 

 coagulated by heat and acetic acid, and the products 

 of protein digestion, if present, are then separated 

 from the coagulated serum proteins by filtration. 

 Great caution must be observed that coagulation is 

 complete and that the filtrate is rendered absolutely 

 clear by a second boiling if necessary. This method 

 does away in a large measure with the difficulties due 

 to haemoglobin-stained sera. We quote the following 

 directions as to the technic from Pearce and Williams* 



