BY R. GREIG SMITH. 291 



saline to remove the serum, after which the suspension was spread 

 over cover-glasses and allowed to dry in the air. The films were 

 stained with recently prepared Leishman stain. The bacterial 

 cells were stained blue and were enclosed in a reddish-coloured 

 matrix — the agglutinated substance. 



The knowledge of the function of agglutination in the question 

 of immunity appears to have advanced but little since Metchnikoff 

 published his work, Immunitdt.* In it he decides against any 

 important role being played by agglutination for several reasons. 

 The chief of these is that it does not appear to be constantly 

 associated with immunity. The agglutinating action of blood 

 serum can be absent in an actively immunised animal, and 

 agglutination may be present and yet immunity be absent. 

 Furthermore, the agglutinating power of the serum in typhoid 

 fever does not increase with the development of immunity. 

 According to Breuer, it remains constant during the height of 

 the disease and during convalescence. That this is not the case 

 is clearly shown by the work of Jorgensen. f The agglutinating 

 power of the serum rises to a maximum and then falls. It was 

 chiefly from these facts that Metchnikoff concluded that agglu- 

 tination is only a side action and is not a cause of immunity. 

 This was in opposition to the views of Gruber and Durham, who 

 supposed that the clumping was caused by the swelling of the 

 membranes of the bacteria whereby they were rendered more 

 susceptible to the action of the bactericidal substance. 



The non-specificity of the Gruber- Widal reaction may be raised 

 against agglutination having an important part to play in 

 immunity. This side of the question has been dealt with by 

 Liidke,J who notes a peculiarity in the behaviour of typhoid 

 bacteria towards agglutinin. Freshly isolated bacteria do not 

 always react with the patient's own serum, while older races 

 show a high degree of sensitiveness. This has been noted by 



* Handb. d. Hygiene (Weyl). Lief.32. Jena, 1897. 



t Centrb. f. Bakt. Orig. xxxviii. (1905), 475, 566. 



X Centrb. f. Bakt. Orig. 1905, xxxviii. 216. 



