koch's circuit. 
Others give the period as from six months to two 
years. 
III. —Some of the blood of the immune animal 
is next obtained; aseptic precautions are observed 
during its removal. After coagulation the serum 
is taken and its protecting power tested on other 
lower animals. 
IV. —It is put up in sterile tubes and carefully 
and aseptically sealed, ready for use of the human 
subject. 
The antitoxin treatment is somewhat similar 
in its effects to vaccination as a protection against 
smallpox. The theory has been advanced that 
vaccination against diphtheria and other com¬ 
municable diseases may come to be an established 
method during epidemics. 
It is claimed by Koch that in order to prove 
that a certain germ or micro-organism is the 
cause of a specific disease it must produce certain 
effects. Briefly, these are as follows: 
I. —Where the disease is present there the 
specified germ must always be found. 
II. —The germ found in the diseased body 
must again grow and multiply in proper culture 
media outside of the body. 
III. —The same disease must be reproduced in 
a healthy animal by using the poison or toxin ob¬ 
tained from the culture media in which the germ 
has multiplied. 
IV. —The same germ must again be found in 
the serum of the blood of the animal thus inocu¬ 
lated as a result of the process. 
Koch further states that it must be proven that 
no other germ is capable of producing the disease 
under consideration and that if the original 
39 
Vaccination. 
Koch’s 
Circuit. 
