150 STUDIES IN IMMUNITY. 



causes swelling, granular transformation and often destruction of 

 the former. If he wished to study the effect of the agglutinin alone, 

 Trumpp evidently should have used fluids that had been previously 

 deprived of the alexin normally present.* Red blood corpuscles 

 clumped by the serum of an animal of a different species seem to 

 keep their normal appearance; they also remain normal when sub- 

 jected to an active anticorpuscular serum that has been previously 

 heated to 55 degrees and thus deprived of its dissolving alexin with- 

 out losing its agglutinin. It seems, moreover, hardly reasonable 

 that such different cells as bacteria and red blood cells undergo 

 the same modifications when affected by an active serum. When 

 we deal with chemical particles such as milk casein instead of cells 

 like bacteria and red blood cells, the existence of a viscous change is 

 still less probable. And yet a serum may be produced that " agglu- 

 tinates" milk, that is to say, which clumps particles of casein. 



Is it reasonable to suppose that these particles become sticky or 

 viscous when affected by the active serum? Is it to be supposed 

 that their sticking together is due to such a viscosity? If we agree 

 to this we must suppose that particles of clay in a homogeneous 

 aqueous suspension are also covered with a special viscous and 

 sticky coating when we add a little sodium chloride to the fluid 

 in which they are suspended. As is already known, the addition 

 of salt to such a fine clay suspension causes flecks to form which 

 settle to the bottom of the tube; this is a fact which interests geol- 

 ogists extremely as a means of explaining sedimentations. 



The existence of an adhesive substance, which is the foundation 

 of both Gruber's and Dineur 's hypotheses, seems to the latter ob- 

 server to be corroborated by a very significant experiment. Dineur 

 has noted that if an emulsion of bacteria to which a specific serum 

 has been added is gently shaken, the clumping of the bacteria 

 is very much increased. Dineur supposes that this mechanical 

 rolling of bacteria tends to bring them together, to interlace their 

 cilia, and to allow the sticky substance with which their cilia are 

 supposedly covered to bring about final adhesion. 



* The same criticism may be made of the statements of Roger (Revue ge*ne"rale 

 des Sciences, 1896) concerning the modification in the oidium albicans subjected 

 to an active serum. Kraus and Seng in a recent article (Wiener klin. Wochen- 

 schrift, 1899, No. 1) have offered the same objections to the experiments of 

 Trumpp and Roger. 



