PHYSICAL CHEMISTRY APPLIED TO THE PHENOMENON OF AGGLUTINATION.

Every one is familiar with the phenomenon of agglutination from the point of view of a diagnostician. When blood or serum from a typhoid patient, for instance, is added in the proportion of 1:50 to a uniform suspension of typhoid bacilli, the bacteria clump together and fall to the bottom of the vessel. The explanation of this clumping has been made the subject of a large number of investigations and many interesting results have recently been presented. In the light of these studies, the phenomenon may be divided into two phases: (1) The union of agglutinin with the bacteria, and (2) the clumping and precipitation of the bacteria thus treated, which may be called "agglutinin-bacteria." Agglutinin-bacteria which have been washed in sterile distilled water and resuspended in distilled water do not undergo spontaneous agglutination as long as no salts of any kind are present in the suspension. The addition of