670 
ROBERT H. WILSON. 
Briefly, antitoxins are formed as the result of the introduc¬ 
tion of toxins. They are so named because they combine and 
render inert their specific toxins. They are biochemical sub¬ 
stances, which are given off from the cells of the body. The 
nature of their composition is as yet undetermined. 
Lysins. The injection of cells, animal, plant or bacterial have 
been found in most cases to stimulate the formation of specific 
antibodies, which have the power of dissolving or breaking up 
these cells. The antibodies are known as cytolysins and are 
usually named with reference to the cause of their production, as 
bacteriolysins, hemolysins, etc. The injection of bacteria produce 
bacteriolysins, red blood corpuscles, hemolysins. Two elements 
known as amboceptor and complement are essential for producing 
the lytic action. 
Opsonins. Antibodies which sensitize bacteria rendering 
them more susceptible to the attacks of the phagocytes. These, 
substances were forcibly brought to the attention of medical 
science in 1902 by Wright and Douglas, as the result of their 
studies on opsonization. 
Agglutinins. Bodies present in the blood and possible other 
fluids of the body of an animal affected with or recovering from 
a specific infectious disease. When a small amount of the serum 
from such an animal is added to a suspension of the correspond¬ 
ing bacteria, the organisms will become agglutinated into clumps 
and precipitated. 
Precipitins. Substances found in antisera which have the 
property when brought in contact with its specific antigen, of 
causing a cloudiness or precipitate. 
The above-mentioned hypothetical bodies are present to some 
extent in normal serum. Infection, natural or artificial, tends to 
increase the amount. 
In order to afford convenience in their description, the bio¬ 
logical products used in veterinary practice may be classified into 
the divisions—vaccines, including bacterins or bacterial vac¬ 
cines—antisera, toxins. 
