16 
through the intervention of a second body, known variousl}" as the 
amboceptor, zwichenkorper, immune body, sensitizer, hxative, pre- 
parative, desmon, etc. 
This order of immunity is particularly evident in the 
poisons that have a lytic or dissolving action upon bac- 
teria or the cells of the bod}", such as the bacteriolysins, 
hemolysins, and other cytolysins. These poisonous 
bodies are believed by Buchner to be a ferment, and 
are usually spoken of as the “ complement,’- but also as 
the ‘‘alexin’' (Buchner) or ‘‘cytase” (Metchnikofl). 
One of the remarkable facts connected with the phe- 
nomena of the lytic poisons is that the poison itself, 
^ ^ , . usuallv called the complement, is normallv present in 
ond order of immu- ^ ‘ ^ 
nity, showing the the blood. The Complement has less resistance to heat 
complement and intermediary bodv, and is therefore spoken of 
immune body. . i ' i -i 
as being thermolalnle. 
According to Ehrlich's theory, immunity can only be obtained 
against the intermediary body, which is believed to be specitic. This 
intermediary body has a greater resistance to heat than the comple- 
ment; that is, it is relatively thermostabile. 
Ehrlich compares the intermediary body with diazo-benzaldehyde, 
which by means of its diazo group is capable of combining with a 
series of bodies, such as aromatic amins, phenols, keto-methyl bodies, 
etc., while l)y means of its aldehyde group it may 
combine with a different series, such as the hy- 
drazins, ammonia radicals, and hydrocyanic acid. 
Phenol and hydrocyanic acid will not directly 
combine, but with diazo-lienzaldehyde acting as 
an intermediary body, these two substances can 
be iirought into combination. Pushing this com- 
parison further, Ave may say that the aromatic 
body, or the phenol, represents a constituent of 
the blood corpuscle. The diazo-benzaldehyde is 
the intermediary body, while the poisonous hy- 
drocyanic acid constitutes the complement. 
Welch ^ A"ery ingeniously extended Ehrlich’s 
conception of immunity to the bacterial cell. 
According to Welch’s views the bacterial cell has the same power of 
defensive action against the poisons produced by the cells of higher 
animals that they have against the toxic i^roducts of the bacteria. 
« Vaughan and Xovy: Cellular toxins, 1902, p. 131. 
^ Welch, William H.; The Huxley lecture on recent studies of immunity with 
special reference to their bearing on pathology. Bull. Johns Hopkins Hosp., Balto., 
V. 13, (141), Dec., 1902, pp. 285-299. 
Fig. If.— The third order of 
immunity, showing an im- 
mune body having two 
aflanities. 
