294 BACTERIOLOGY 



their defensive powers by a substance, "aggressin," elabo- 

 rated by the invading bacteria. While Kikuchi, accepting 

 the "aggressin" doctrine, restricts the action of "aggressin" 

 to the leukocytes and interprets it as in the nature of a 

 negative chemotactic phenomenon, whereby the leukocytes 

 are so repelled that they cannot approach and take up the 

 bacteria. 



The efforts of Wright and Douglass have been in the way 

 of accentuating phagocytic activity and their results have 

 shed a flood of most important light upon the subject. In 

 1903 and 1904, in papers presented to the Royal Society 

 of London, they express the opinion that leukocytes alone 

 are incapable of taking up bacteria, and that in order for 

 them to exhibit this function the bacteria must first be 

 acted upon by a something contained in the normal 

 blood, a state of affairs analogous to that observed by 

 Pfeiffer. They conceived this preparation of bacteria 

 for ingestion by leukocytes to be in the nature of the pre- 

 paration of food for consumption. They employ the term 

 "Opsonin," (meaning to cater for; to prepare food) in 

 designation of the element in the blood having that property. 

 Prior to the observations of Wright and his associates it 

 had been known that if white blood cells be washed free of 

 all adhering serum they are incapable of taking up bacteria, 

 but the interpretation, in the light of Wright's work, seems 

 to be incorrect. It was believed that a something in the 

 blood, a "stimulin" as it was called by some, acted not on 

 the bacteria but on the leukocytes, stimulating them to 

 activity. Wright and his colleagues have clearly shown the 

 error of that view and have convincingly demonstrated that 

 it is the action of their "opsonin" on the bacteria that makes 

 phagocytosis possible. Thus, for instance, if bacteria and 



