238 
NOCARD AND ROUX. 
by the exchanges which go on through the wall of the sac; it 
becomes slightly albuminous ; and above this obtains the quality 
of becoming useful for the culture, in vitro^ of the pleuro-pneii- 
monic microbe. 
Once we have obtained by the inoculation of a few drops of 
pleuro-pneumonic serosity in peptone bouillon freshly prepared 
a culture similar to that of the bags. At least, the bouillon 
presented after remaining 72 hours in the thermostat the very 
slight opal aspect and the motile and refringent points which 
characterize this culture. But we were not able to renew the 
experiment, nor to make a second culture from that which we 
had obtained by chance. 
This observation, however, confirmed us in the idea that the 
pleuro-pneumonic virus can be cultivated outside the organism. 
What was required was to find a proper media for the culture. 
We succeeded after long researches. The fluid which has given 
us the best results is made by the addition of a very small quan¬ 
tity of rabbit or cow serum to the peptone solution, prepared by 
Mr. Louis Martin, to obtain large quantities of diphtheric tox- 
ine. The proportion of serum must not be above one-twenty- 
fifth (about 4 drops for 5 c.c. of the solution). No culture is 
obtained if the peptone solution of Witte or that of Chapoteau 
is used ; and again culture does not take place in presence of 
inert gases or in vacuum. 
The bouillon Martin serum not only allows the keeping up 
of the culture started during the sojourn in the collodion or 
reed-cane bags ; it may also give a culture from the start, when 
it is inoculated with a trace of natural serosity. 
Culture in vitro of the microbe of pleuro-pneumonia consti¬ 
tutes a great progress ; it will be possible to study its toxine, try 
to modify its virulency ; it always presents this advantage to 
preserve* the pleuro-pneumonic virulency intact, while it has 
seemed to us that successive passages through the organism of 
the rabbit diminish it in a sensible manner. But the degree of 
receptivity to the pleuro-pneumonic virus varies so much, even 
in individuals of the same age and same breed, that we do not * 
