166 Messrs. 8. G. Shattock and L. 8. Dudgeon. [Dec. 21, 
It might be at first assumed that the heightened index showed that the 
“increased phagocytosis is due to the presence of a cytotropic substance exclu- 
sively, seeing that melanin, not being bacterial, cannot (so it might be supposed) 
be susceptible to the action of a bacteriotropic or opsonic substance. This, 
however, is not the case. The proof of this we will adduce later on, but 
briefly it consists in this, viz, that an immune serum can be largely 
deopsonised by means of melanin if the latter is used to saturation. And if 
melanin can deopsonise, it can only do so by becoming opsonised. We 
believe that in both cases the result so obtained is mechanical; the finely 
divided substance, though inert, entangling or becoming invested with the 
still more finely particulate material, of which the opsonin would thus appear 
to consist. 
In the six following observations, the ordinary method of estimating the 
opsonin index was carried out, 2.2, normal washed leucocytes were used : 
(1) in normal serum ; (2) in the patient’s serum. 
The cases comprised :—Acute pneumonia, lymphangitis, pneumonia, acute 
pneumonia with pleural effusion, urinary fever (colon bacillus infection), 
empyema. 
Renarks on the Six Foregoing Observations. 
The index in the third and fourth cases was taken by Wright’s method, and 
also by the simpler one of using normal blood against the blood of the 
patient. The index obtained by the second method is in both cases higher, 
being 1:2, as compared with 1; and 4°7 as compared with 1. 
Question 2.—Will saturation of an immune serum with melanin remove the 
r) 
““opsonin” and reduce the phagocytosis of normal cells against either the 
bacillus or a suspension of melanin, or against both? That is to say, how far 
are “ opsonisation ” and “ deopsonisation ” strictly specific ? | 
In the following observation the action of the patient’s cells in the 
presence of melanin is compared in the patient’s serum, and in the patient’s 
serum after saturation with melanin. The serum was digested with a thick 
suspension of melanin for 24 hours, at 37° C. 
CasE.—Acute appendicitis ; peritonitis ; due to B. colv. 
1 vol-cof the patientis: washed! cellesi11.& .gacssseee eee eee eee 50 cells 
1 e e SOLU cine asin nestle ne omen eee eerie eeneares } contained 
1 Pr MMOIAM ise Agee ae ences va\b.sin'n ecacacpvisin. ste POR RES erento 68 granules. 
I yol,ot the patient's avashed cells. (7) 1yayvanceeeeceeneenecee secre 50 cells 
il a Me serum after saturation with melanin } contained 
1 AP PU ICAL PIN Eee rene ARMOR OR REMRE EEE fi 5cn sho BLALLoaNsg cnocHue eu 28 granules. 
The phagocytosis was reduced to nearly one-third. 
