379 
Agglutination of Spirochaetes 
Inject a rabbit, intravenously, on two or three 
occasions with S~i c.c. of spirochaete blood. Its serum 
will now agglutinate, render motionless and transform 
into granules the corresponding spirochaete, but has no 
action on other spirochaetes. Agglutination will occur 
up to dilutions of I in ioo. 
Pfeiffer’s Phenomenon 
Inject a mouse, intraperitoneally, with o*i c.c. 
of a specific spirochaete serum and f c.c. of blood 
containing the corresponding spirochaete. The spiro¬ 
chaetes disappear from the peritoneal cavity in ten 
minutes, and the mouse does not become infected. If 
any other but the corresponding spirochaete be used, 
the spirochaetes are not destroyed and the mouse 
becomes infected in twenty-four hours. 
^ rAn 
Fig . 116 Sp. lave rani 
5. Sp. laverani (Breinl, 1907).—In the blood of 
white and wild rats. In the fresh state it is an extremely 
small, active spirochaete, shooting across the field, 
revolving, turning, like a very active motile vibrio, and 
not like other spirochaetes. Stained, it has two to six 
spirals and is 2-6 ^ in length (Fig. 116). 
They are transmissible to mice and young rats only. 
The infection may persist for months, though the 
number of spirochaetes is then very small. 
