Febbuary 12, 1909] 



SCIENCE 



243 



Bacteria or corpuscles are not necessa- 

 rily altered in opsonic serum and many 

 bacteria, notably streptococci, pneumo- 

 cocci, anthrax bacilli, as well as others, 

 grow freely in such serum. Heretofore 

 the belief that phagocytes may cause de- 

 struction of bacteria rested largely upon 

 more or less convincing morphological ap- 

 pearances. By means of the plate method 

 for demonstrating bactericidal action it 

 now has been shown conclusively that cer- 

 tain bacteria that do not suffer demon- 

 strable injury by blood serum alone, such 

 as those just mentioned, undergo intra- 

 phagocjiiic destruction when put into mix- 

 tures containing living leukocytes and 

 opsonically active serum. In serum alone 

 and in suspensions of serum-free leuko- 

 cytes active growth occurs, but when the 

 two are mixed destruction takes place, 

 other factors being equal, in proportion to 

 the number of leukocytes present. The 

 actual demonstration of phagocytic an- 

 nihilation of bacteria, formerly so often 

 demanded by the opponents of the phago- 

 cytic theory, is here furnished. 



The indications are that various opson- 

 ins with more or less well-marked specific 

 affinities occur in all animals down to and 

 including the echinoderms, being, like 

 other antibodies, present to a variable ex- 

 tent in normal blood and other fluids. 



In the course of his studies on lymph 

 formation Professor Carlson^ finds that 

 opsonins and related bodies are more con- 

 centrated in the serum than in the lymph, 

 that their concentration varies in the 

 lymph from different organs, and that 

 their apparent relative concentration in 

 different lymphs also varies. The fact 

 that the relative concentration is not the 

 same in all lymphs speaks of course 

 strongly in favor of the antibodies being 

 distinct substances, a point concerning 

 which there is still difference of opinion, 



^ Personal communication. 



some believing that it concerns different 

 modes of action of the same body, others 

 that each action is dependent upon a dis- 

 tinct body. 



At first opsonins were regarded as sub- 

 stances of a relatively simple structure, 

 quite easily destroyed by heat (60° C. for 

 15 to 30 minutes) and other agents. But 

 it has been found that in most cases the 

 total opsonic effect of fresh serum is the 

 result of the combined action of two 

 bodies, one relatively resistant to heat, the 

 other easily destroyed by heat. The heat- 

 resistant element is capable of opsonic 

 action by itself and seems to unite quite 

 firmly with the object upon which it acts; 

 the opsonic effect as measured by the re- 

 sulting phagocytosis is, however, greatly 

 promoted on the addition of the other, 

 thermolabile element, which alone has no 

 opsonic power. In other words, opsonins, 

 as a rule, seem to have the same duplex 

 constitution as the lysins with which they 

 are held by some to be identical. 



The heat-resistant opsonic element ap- 

 pears to attach itself firmly to the bacte- 

 rium or corpuscles upon which it acts be- 

 cause, in some instances at least, it is not 

 detached even after many washings of the 

 opsonified bacteria or corpuscle in large 

 quantities of salt solution. Consequently 

 opsonification is to be regarded as the 

 special action of a distinct unit and not as 

 the result of the influence of plasma or 

 serum as a whole. The thermolabile, acti- 

 vating element, however, according to 

 the results of recent experiments, probably 

 remains free in the fluid of the phagocytic 

 mixture, and there seems to me to be good 

 room still for question as to whether its 

 effect is exercised upon the phagocytable 

 object or upon the phagocyte. Years ago 

 Metchnikoff expressed the view that serum 

 may stimulate leukocytes and other cells 

 directly to phagocytosis, while, on the other 

 hand, bacteria or red blood corpuscles that 



