1891.] Wandering Cells in Animal Bodies. 517 
water crustacean. He found that many of these animals, which 
he kept in an aquarium, were very liable to be attacked by the long, 
needle-like spores of a certain fungus. These, once established 
in the tissues, multiplied and often caused the death of the animal. 
The spores first obtain a position in the intestine. By degrees 
they work their way through its walls, and appear in the body- 
cavity. As soon as this happens, phagocytes appear on the scene 
in great numbers, and attack the invaders. If these can only be 
killed, they will be rendered ,harmless, for then their breaking 
down can be accomplished, and they can be removed. But if 
they are too numerous, some will escape uninjured, and, finding 
themselves under suitable conditions, will sprout and grow, and 
this means the death of the 
individual. It will be seen 
by Figure 2 that one of 
these spores is several times 
larger than a leucocyte, and 
though the latter is capable 
of great distension, it may 
not be able alone to dispose 
of a spore. In such a case, 
two or more may invest dif- Spores and blood of ro bat ra 
ferent parts of the same 
enemy, But a more effectual coöperation may: be secured in this 
remarkable way. Several cells may become fused into one great 
mass, forming a single individual of sufficient size to surround a 
spore and kill it, When this has been accomplished, the spore S008 
loses its original shape, and finally falls to pieces. These differ- 
ent stages are shown in Figure 2. This united effort of the 
phagocytes may thus prevent disease ; though very often, when 
the invasion is too great, they are not able to stem the tide, and 
the animal dies. : 
Still following, for the present, the experiments of Metschni- 
koff, we may notice a few observations made upon verte- 
brates. The microörganism of splenic or relapsing fever is as 
large bacillus, and favorable for study on this account, for bacteria 
appear as extremely small objects, even when magnified as greatly 
Fig. 2 
