Combining Properties of the Opsonin of an Immune Serum. 187 



anti-toxic or anti-cellular action, but we are far from denying the possibility 

 that such an action may be obtained. 



The phagocytosis of formed cellular elements plays an important role in 

 inducing resistance ; serum is impotent to produce resistance, blood corpuscles 

 do so. The energetic phagocytosis which accompanies the spontaneous 

 absorption of transplanted tumours, and which occurs in absorption after 

 exposure to radium, speaks strongly for the conclusion that the processes are 

 the same in kind when blood or tumour cells, being absorbed, produce 

 resistance. But we are as yet unable to determine the extent to which 

 agencies directed against the tumour cells themselves may assist in 

 determining their early death in protected animals. Other experiments 

 still in progress may be expected to clear up the relative importance of the 

 parts played by the hypothetical inhibition of the specific stroma reaction, or 

 of an equally hypothetical direct lethal action on the tumour cells. 



On the Combining Properties of the Opsonin of an Immune 



Serum* 



By Eobert Muir, M.D., Professor of Pathology, University of Glasgow, 

 and W. B. M. Martin, M.B., Carnegie Eesearch Scholar. 



(Communicated by Dr. C. J. Martin, F.K.S. Eeceived January 18, — 

 Read February 7, 1907.) 



In a recent publication! we have studied the combining properties of the 

 thermolabile opsonins of normal sera, and have shown that various substances 

 or combinations of substances which absorb serum complements also absorb 

 the opsonins in question. Of special interest is the fact that red corpuscles, 

 and also heated normal sera, which by themselves have no appreciable 

 effect either on complements or on opsonins, absorb or fix both of these 

 bodies when combined with their corresponding anti-substances, immune- 

 bodies and precipitins respectively. Since the time of this publication we 

 have extended our experiments, and have always obtained the same result — 

 the opsonin is always fixed when the complement is fixed. Using the term 

 complement in the bio-chemical sense, we have said that the normal thermo- 

 labile opsonins belong to the group of complements. And we have also 



* Towards the expenses of this research a grant was received from the Carnegie 

 Trustees, for which we have pleasure in recording our indebtedness, 

 t Muir and Martin, ' Brit. Med. Journ./ 1906, vol. 2, p. 1783. 



VOL. LXXIX. — B. Q 



