437 
dark red with Giemsa, the other light blue, with apparently no 
chromatic core, but showing an irregular number of dark red granules 
situated at the points at which the two spirochaetes were in 
apposition. We are inclined to explain this appearance as 
conjugation. 
Prowazek describes intra-cellular stages of Spirochceia gal l in arum 
in the red blood cells. We were able to observe the same phenomenon 
in rare instances with SpirocJurta duttoni just before the crisis set in 
(%• n). 
Although the appearance of the parasites in the peripheral blood 
seemed fairly uniform, striking changes were observed in parasites 
seen in the organs, notably in the spleen, bone marrow, and liver. 
Numerous spirochaetes, especially just before the crisis, when the 
blood was still swarming with parasites (principally in the spleen and 
bone marrow, rarely in the liver), were seen coiling themselves up 
1% I 2 ), a few presenting a swollen appearance (fig. 13), the majority 
gradually becoming thinner and rolling themselves up into more and 
more complicated skein-like forms (figs. 14, 15) which seemed to 
become more irregular as the time of the crisis drew near The 
majority of these forms were devoured by the phagocytes of the 
spleen, and at the time of the crisis the spleen cells were observed to 
be gorged with degenerated spirochaetes. In animals in which the 
spleen had been removed an analogous process took place in the liver. 
A few similarly shaped parasites underwent a remarkable 
change:— The outline remained more regular for a time, and the 
parasite surrounded itself with a thin cyst wall, the interior of the 
c .vst being filled with a faintly blue stained plasma (fig. 16). These 
knns, in scanty numbers, were to be seen even after all the other 
krrns had disappeared. They apparently undergo further changes, 
as the shape of the parasite becomes more and more indistinct and, 
at a still later stage, only the cyst filled with small red granules 
Persists. 
We were unable to trace the further development of these forms, 
as in specimens stained by Giemsa’s method it is impossible to 
differentiate them from blood platelets and other constituents. The 
'act that the filtrate of spirochaetal blood through a Berkfeld filter is 
infective suggests that these small granules may be the forms which 
Pass through the filter and give rise to a fresh infection. 
