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ANNALES DE L’INSTITUT PASTEUR 
at 37°C. The virus was taken from lhe stock of glycerinated, carbolized, calf 
virus as distributed by the Board of Health of New York City. It was dia- 
lyzed through collodion sacs in sait solution, and placed in the ice-box to 
allow coarse particles to sédiment. Only the supernatent fhiid was used, 
and diluted with Ringer’s or sait solution, thus a fairly uniform émulsion 
was obtained. 
To demonstrate the activity of the virus, we adopted the 
method of Calmelte and Guérin [3J. 
They hâve shown that the virus ruhhed on the freshly shaven 
skin of a rahhit produces a typical vaccinia éruption. Fur- 
thermore, they hâve shown, hy increasing dilutions, that the 
number of vesicles in the éruption indicates fairly accurately 
the quantity of virus présent. This method is largely used iu 
commercial laboratories ior standardizing the strength of the 
virus. 
In our experiments the skin of a rabbit was inoculated with 
a small number of freshly put up, unincubated préparations. 
Similar inoculations were made later with incubated prépara¬ 
tions ; the pustules counted in each instance and the two reac¬ 
tions compared. 
When cornea was the tissue used , we fourni a definite increase 
of the virus after incubation of 7 to 18 dctys. 
The unincubated préparations produced éruptions varying 
from 10 to 50 pustules , while lhe “ takes ” from the incubated 
préparations were confluent , estimated at 200 to 250 pustules. 
As in the confluent éruptions the number of pustules could 
not be counted, only estimated, to détermine more closely the 
cxtent of multiplication, higher dilutions of the virus were 
used in the original préparations. 
H ere the unincubated préparations gave 6 to 10 flcit pustules ; 
the préparations incubated 11 days gave 55 to 65 elevated pus¬ 
tules. 
We find, therefore, that while there is a definite increase 
in the virus in plasma préparations containing living cornea, 
this multiplication is not comparable to that observed in cul¬ 
tures of rapidly growing bacteria. Many viruses hâve been 
tested in the préparations and almôst ail hâve shown multipli¬ 
cation, rarely, however, one is found which does not grow. 
From the active préparations, suhcultures hâve heen made 
