376 
DK. AHHIGO VrSENTINI. 
by chloroform at various intervals of time from the first 
injection, fi-om an hour and a quarter to ninety-three days 
after, and the autopsy was performed immediately. Both 
the guinea-pigs and the rats showed no signs of loss of flesh ; 
some of them were even increased in weight. While they 
were still living, with a glass pipette having one end drawn 
out into a capillary tube I took from the peritoneal cavity a 
drop of yellowish liquid, slightly turbid, containing, as we 
shall see further on, numerous leucocytes, chiefly mono- 
nuclears. 
The subsequent autopsy revealed nothing noteworthy ; the 
internal organs, spleen, liver, kidneys, bone-marrow and 
lungs were not increased in volume or chatiged in appear- 
ance or iu any way different from those of healthy animals. 
Of these organs I made smears which I fixed afterwards 
either in methyl alcohol or with osmic acid vapour and 
absolute alcohol and stained with Giemsa’s stain. The most 
careful examination has never enabled me to discover a 
Leishmania, either in its usual form or in the flagellate 
leptomonad or other type, even when the autopsy followed 
close upon the inoculation of the cultures into the peri- 
toneum. 
Both of the blood and of the internal organs I have tried 
in each animal numerous cultures in blood-agar (method of 
Novy and Nicolle), and 1 have never obtained development 
of Leishmanias; the culture-tubes remained perfectly sterile, 
save for some rare exceptions (see below). 
1 think, therefore, that I am able to establish the point that 
guinea-pigs and rats possess a natural immunity against the 
cidtural forms of the Leishmania of the Mediterranean basin, 
alike whether the strains are recently isolated or of long 
standing and whether the cultures are new or old sub- 
cultui-es. 
i'he case of the infection of the guinea-pig obtained by 
Franchini with cultures remains, therefore, unique and must 
at least represent a somewhat rare event. It was a case 
perhaps of a single animal extraordinarily and exceptionally 
