200 CLINICAL BACTERIOLOGY AND H/EMATOLOGY 



ESTIMATION OF THE OPSONIC POWER. OF THE 



BLOOD 



A very important branch of blood-work, and one that seems 

 destined to be of great value in the future, has been intro- 

 duced by Wrig'ht, who has demonstrated the presence in the 

 blood of substances which he calls opsonins, and which have 

 the power of acting on pathogenic bacteria and altering them 

 so that they can be taken up and digested by leucocytes. 

 These substances are of great importance in that they appear 

 to be the chief agents in the production of some forms of 

 immunity. Take, for instance, the defence of the body against 

 staphylococci. Leucocytes have no power of taking up these 

 organisms, and if the protection of the body were entrusted 

 to them alone a slight staphylococcic lesion would be a very 

 serious matter. But the blood contains a certain amount of 

 antistaphylococcic opsonin a greater amount in some per- 

 sons and less in others and this, by combining* with the 

 staphylococci, renders them easily attacked by the leucocytes. 

 It follows that where we can measure the amount of opsonin 

 present we can form some estimate of the patient's resisting 

 power against the organism in question. It is found, for 

 instance, that the serum of patients in the early stages of 

 staphylococcic diseases, such as pustular acne or boils, is 

 usually very deficient in antistaphylococcic opsonins, whilst 

 when cure takes place the amount rises above normal. These 

 opsonins are probably specific i.e., each organism has its 

 own appropriate opsonin : that for tubercle, for example, is 

 devoid of action on staphylococci, and vice versa. 



The method given is practically that used by Wright. It is 

 a general method, and is available for almost any organism, 

 the only points of difference arising in the preparation of the 

 emulsion of bacteria, which differs somewhat with the various 

 organisms. The method is a relative one. Two tests are 

 made, one with the serum of the patient, and one with that 

 of a healthy person, and the results of the two are compared 

 in the manner to be described subsequently. 



The process is not altogether an easy one, and requires a 

 considerable amount of patience and some practice. Yet I 

 know that several practitioners have been able to accomplish 



