314 INFECTION AND RESISTANCE 



In this point it is not unlikely that Wright is mistaken, since 

 other observers, notably Lohlein, 12 have observed the phagocytosis of 

 various bacteria by washed leukocytes in indifferent, opsonin-free 

 media. Although we may take it as assured that such spontaneous 

 phagocytosis may take place (Metchnikoff and a number of others 

 having obtained results similar to those of Lohlein), this is prob- 

 ably never very intense. 



In fact, Wright, in some of his later work, does not insist rigidly 

 upon the non-occurrence of spontaneous phagocytosis, but attempts 

 to associate such phenomena with the salt contents of the medium 

 in which it occurs. Together with Reid, 13 he determined that spon- 

 taneous phagocytosis of tubercle bacilli unquestionably takes place, 

 is most intense at a concentration of about 0.6 per cent. NaCl, and 

 diminishes as the concentration is increased. This, as we shall see, 

 has bearing on the possible physical explanations advanced to ac- 

 count for opsonic action, and has its parallels in experiments on the 

 (influence of electrolytes on agglutination and precipitation. 



The fact remains that Wright demonstrated by his work that 

 MetchnikofFs original view, which interpreted the difference be- 

 tween susceptibility and immunity as a difference between the in- 

 herent phagocytic powers of the leukocytes, is incorrect, and that 

 the essential regulating influence affecting phagocytosis rests upon 

 the action of the serum upon the bacteria. 



The following experiment from the work of Hektoen and Rue- 

 diger 14 illustrates this point with exceptional clearness. It shows 

 that human leukocytes in the presence of normal defibrinated blood 

 will take up bacteria energetically. When the leukocytes, however, 

 are washed free of blood and added to untreated bacteria phago- 

 cytosis is practically nil. If, however, such washed leukocytes are 

 mixed with bacteria that have been previously in contact with serum 

 active phagocytosis will take place. In other words, the bacteria 

 have been altered by the serum in such a way that they are now 

 amenable to phagocytosis by washed leukocytes. The serum then 

 acts upon the bacteria and not upon the leukocytes. 



TABLE II 



Phagocytosis by Human Leukocytes of Sensitized Bacteria 



Average 

 Phagocytosis 



Human leukocytes (defibrinated blood) + Staphylococcus aureus 22 . 



Human leukocytes (washed in NaCl solution) + Staphylococcus aureus. 1 . 2 

 Human leukocytes (washed in NaCl solution) -f Staphylococcus aureus 



(treated with human serum) 10 . 



Human leukocytes (defibrinated blood) -f Streptococcus 300 22 . 



12 Lohlein. CentralbL f. Bakt., 38, 1906, Beihef t, p. 32 ; also Munch, med. 

 Woch., 1907, p. 1473. 



is Wright and Reid. Proc. of Royal Soc. B., Vol. 77, 1906. 



14 Hektoen and Ruediger. Jour. Inf. Dis., Vol. 2, 1905, p. 132. 



