154 PROCEEDINGS OF SECTION B. 
0-00005 grm.) can be detected as give a scarcely-perceptible 
deposit in Marsh’s test. 
These are but a few examples of how the action of micro 
organisms come within the province of the chemist in the 
laboratory. 
The Products of Pathogenic Bacteria. 
Certain pathogenic bacteria modify the albuminoid media 
in which they are cultivated into substances of a poisonous 
nature. These are known as toxines, and as each bactertum 
produces a specific poison, the toxine generally bears a name 
derived from the bacterium, or of the induced disease, as, 
for example, mallein (from Bact. mailer, the glanders bac- 
terium), diphtheria toxine, &c. Tuberculin is perhaps the 
toxine most extensively manufactured, and the method em 
ployed is generally applicable for the preparation of other 
toxines. 
Tuberculin—Old and New. 
Tuberculin is neither more nor less than a concentrated 
and sterile glycerine-broth culture of the tuberculosis bac- 
terium. The broth generally consists of meat extract, pep- 
tone, and common salt, with the addition of 7 per cent. 
glycerine. On such a sterile broth fragments of ‘an old and 
pure culture of the bacterium are floated, and the vessels are 
incubated at 37° C. for several weeks, until a maximum 
toxine formation is obtained. The culture is then boiled, 
filtered, and evaporated down to one-fifth. It is thus a 
solution of the toxine in 35 per cent. glycerine, which acts 
as a preservative. . 
This process of manufacture is rather costly, and a step 
in a forward direction was made about two years ago, when 
it was announced that the toxine of the tuberculosis bac- 
terium was simply a dilute solution of an alkaline succinate, 
If such is the case, the toxine which formerly cost pounds 
could be obtained for as many pence. But nothing more 
has apparently been done with the discovery. and it there 
fore lacks confirmation. 
There is another and newer form of the toxine on the 
market, with the designation Tberculin, T.R. While the 
old tuberculin consists of the excreted products of the bac- 
teria soluble in glycerine, the new contains only the sub- 
stances within the bacteria. The method employed in 
extracting the endocellular toxines from the tubercle bac- 
terium may be taken as a general process, and is approxi- 
mately as follows:—A well-dried culture is broken in a 
mortar, and placed upon one of two very closely set steel 
