66 
PRINCIPLES OF BACTERIOLOGY 
tion on shaking. If both tubes one and two do not 
show hemolysis or agglutination, the blood of the donor 
is suitable for transfusion; if either tube one or two 
shows hemolysis (disappearance of red blood cells and 
the contents of the tube assuming clear golden or Bur¬ 
gundy color) or agglutination (as shown by cell clumps 
not disappearing on vigorous shaking) the donor’s blood 
is not suitable for transfusion. 
Moss’s Classification.—When transfusion must be done 
at once, and every hour counts, then a very rapid method 
of blood matching must be resorted to. 
The work of Landsteiner, Jansky and Moss has estab¬ 
lished that all human bloods belong, so far as agglutina¬ 
tion is concerned, to one of four groups. 
Blood serums of each group are kept in stock; the 
donor’s red blood cells are added to a drop of each of 
the four serums on a glass slide, and, under the micro¬ 
scope, one easily determines which type the blood be¬ 
longs to. The donor and the recipient must belong to 
the same group; remember that in spite of the state¬ 
ments that group 4 is a universal donor (that is, the 
blood of one who belongs to group 4 may be used for 
transfusing the person who belongs to any group), se¬ 
vere reactions have followed its use. Always have the 
recipient and the donor belong to the same group. 
VI. Theories of Immunity 
There are two distinct explanations offered to account 
for the various phenomena of immunity, one of Metch- 
nikoff, called “cellular theory” (because he ascribes the 
most important part to the action of various cells of the 
body) or “theory of phagocytosis” (from Greek pliagein, 
meaning to eat and Icytos meaning a cell) ; and the other 
of Ehrlich, called “humoral theory” because the greatest 
