Abstract
A study of 22 haemagglutinating viruses was made to see whether by treating the viruses and the receptors on the red cells with a variety of physical and chemical agents, a convenient means could be devised for identifying and classifying these viruses, while throwing some light on the chemical basis of the haemagglutination reaction. The viruses were submitted to 13 different treatments; acid, urea, p-chloromercuribenzoic acid, deoxycholate and possibly bi- sulphite might be useful for the classification of unknown agents since they gave similar results with all members of a biological group. Other treatments (e.g. formaldehyde) gave results which varied from strain to strain in such a group of viruses and might be useful for genetic studies. The red cells were treated in nine different ways; formalin, papain, chymotrypsin, periodate, receptor-destroying enzyme, (RDE) and swine influenza virus each prevented agglutination by one or two viruses (apparently by inactivating cell receptors). These results were complementary to those with the virus haemagglutinins. The importance of standardized conditions of test are emphasized.