He also showed that the development of artificial immunity is attended by the appearance of phagocytosis; also, when an anti-serum is injected into an animal, the phagocytes which formerly were indifferent might move towards and destroy the bacteria.
This opsonin of normal serum is very labile, being rapidly destroyed at 55° C.; that is, a serum heated at this temperature has practically no greater effect in aiding phagocytosis than normal salt solution has.
The behaviour of certain cells, especially leucocytes, with regard to anti-bacterial sera, the presence of phagocytosis cannot be regarded as the essence of immunity, but rather the evidence of its existence.
There they show marked phagocytosis, attacking and taking up into their interior and destroying the micro-organisms in large numbers.
The work of Metchnikoff, dating from about 1884, has proved of high importance, his theory of phagocytosis (vide infra) having given a great stimulus to research, and having also contributed to important advances.
Wright and Douglas showed that under these conditions phagocytosis might occur when a small quantity of normal serum was present, whereas it was absent when normal salt solution was substituted for the serum; the latter thus contained substances which made the organisms susceptible to the action of the phagocytosis.
A particular bacterium had a special action in bringing about phagocytosis of that organism, and it had been found that this property was retained when the serum was heated at 55° C. It is now generally admitted that at least two distinct classes of substances are concerned in opsonic action, that thermostable immune opsonins are developed as a result of active immunization and these possess the specific properties of anti-substances in general, that is, act only on the corresponding bacterium.
Then as regards natural powers of destroying bacteria, phagocytosis aided by chemiotaxis plays a part, and it can be understood that an animal whose phagocytes are attracted by a particular bacterium will have an advantage over one in which this action is absent.
Metchnikoff showed that in animals immune to a given organism phagocytosis is present, whereas in susceptible animals it is deficient or absent.
In the light of all the facts, however, especially those contains an opsonin which leads to phagocytosis of the bacillus, and the latter is then destroyed by the leucocytes.
But their disintegration is more commonly brought about by " phagocytosis " on the part of the phagocytic cells in the different organs concerned with the function of haemolysis, i.e.
A further application of the facts of chemiotaxis and phagocytosis has been made by Metchnikoff to the case of Inflammation.
Ersten Entwicklungsphasen einiger Cynipidengallen (Amsterdam, 1882); Bordet, " Phagocytosis," Ann.
If either of these is wanting or interfered with, phagocytosis will necessarily fail as a means of defence.
On reaching the vicinity they leave the blood stream and join in the warfare - many performing their function of phagocytosis (q.v.), others falling victims to the toxins.