984 
if a colony of mould made its appearance 
on the gelatin plate, colonies of B. icteroides 
immediately sprang up around it. After 
some days the colonies of B. icteroides form a 
sort of constellation around the mould, the 
most abundant development taking place in 
the immediate neighborhood of the latter. 
This observation was experimentally veri- 
fied with six species of moulds (not named) 
‘accidentally isolated’ in the laboratory, all 
of which proved themselves, although in 
different degrees, capable of favoring the 
revivification and multiplication of the 
yellow fever germ. To this singular sym- 
biotic relation Sanarelli is inclined to at- 
tribute the ready domiciling of the disease 
on shipboard and its connection with 
warmth, moisture and darkness, conditions 
which, by directly favoring the germination 
of moulds, indirectly favor B. icteroides. 
In some brief notes upon the resistance 
of the germ to physical and chemical agents 
it is stated that, by exposure of broth cul- 
tures to 55°, the germ is killed in about 
twenty minutes, and thatit is instantly de- 
stroyed by a temperature of 65°. Dry heat 
at 110°—125° is speedily fatal, and exposure 
for one hour and ten minutes at 100° also 
suffices to destroy vitality. Considerable 
resistance is shown to desiccation, a result 
of evident practical importance. In sea 
water the bacillus shows great vitality, sur- 
viving in the sterilized brackish water of 
the La Plata for upwards of ninety days. 
Sanarelli’s third memoir is devoted to a 
consideration of immunity and serum 
therapy. The serum obtained from the 
bodies of yellow fever victims causes agelu- 
tination of B. icteroides, although the inten- 
sity of the reaction is said to be quite vari- 
able. This serum does not exert any 
protective power in inoculated animals. 
Serum from a convalescent provoked a 
tardy agglutination and manifested a slight 
preventive power. 
An attack of yellow fever in man confers 
SCIENCE. 
[N.S. Von. VI. No. 157. 
some degree of immunity against a second 
attack, and hence it would seem as if it 
might be possible in some way to vaccinate 
animals against the disease. Attempts to 
produce immunity in the rabbit failed on 
account of the excessive sensibility of this 
animal to the yellow fever virus, and the 
same difficulty prevented the use of the goat 
and the sheep. The work upon immuni- 
zation was mainly limited, therefore, to ex- 
periments upon the guinea-pig, the dog and 
the horse. In all these animals immuniza- 
tion is an unusually difficult and laborious 
task. While it is possible to immunize a 
guinea-pig against cholera or typhoid fever 
in from two to three months, it needs six 
to seven months of assiduous and delicate 
work to vaccinate this animal against yel- 
low fever. Dogs may be immunized some- 
what more readily, but never become tol- 
erant of large doses of toxin. Horses are 
treated first with small doses (5-10ce.) of 
a filtered culture of the germ injected sub- 
cutaneously, followed with intravenous in- 
jections. After two months of treatment 
with filtered cultures the more potent doses 
of cultures sterilized by ether may be used; 
it is not until five to six months after the 
beginning of the treatment that the first 
injection of a living culture may be safely 
hazarded. During this process of immuni- 
zation many of the animals die and all are 
profoundly affected. 
The serum of animals immunized in this 
way is endowed with protective and cura- 
tive properties and can be used with suc- 
cess in animal experiments. A single in- 
stance may serve to illustrate the results 
obtained by this procedure. A horse under 
treatment for the space of nine months re- 
ceived subcutaneously during this period 
29ec. of filtered cultures and 350ce. of cul- 
tures sterilized with ether, and intrave- 
nously 2640ce. of sterilized cultures, 345cc. 
of living broth cultures and 19ce. of an 
agar culture. The serum (0.5cce.) from this. 
