BIOLOGICAL PRODUCTS. 
287 
Many curious phenomena are observed in growing- large cul¬ 
tures for any of these purposes. One of the most annoying is 
the ease with which large cultures of certain bacteria become 
contaminated while very crude bacteriological technique will 
suffice in preventing contamination where other organisms are 
used. In the preparation of tuberculin, contaminations are rare 
while the opposite is true when dealing with Bacillus mallei in 
the preparation of mallein. Large cultures of diphtheria are also 
contaminated with organisms which seldom or never appear in 
other special or routine work where the same incubating cham¬ 
ber is used. These occurrences are difficult to explain. I have 
considered that the aroma coming from a large culture has an 
important bearing on this feature. All bacteriologists are fam¬ 
iliar with the odor coming from cultures commonly seen in any 
laboratory and we similarly have distinct characteristic odors 
given off from cultures of Bacillus mallei, Bacillus diphtheric?, 
bacillus tuberculosis and others. So important are these odors 
that a laboratory worker with a delicate olfactory organ can dis¬ 
tinguish a pure from an impure culture. Under such conditions, 
where we have no diagnostic method of staining I consider the 
microscope examination a confirmatory procedure and not a 
primary factor. I am further of the opinion that the aroma has 
a direct relationship to the efficacy of any of these bacterial 
products. 
Normal sera, or the sera from a normal or untreated animal 
may be used with more or less benefit in diseased conditions 
which are but slightly or wholly non-infective to the animal 
from which they are taken, such as normal horse serum for 
tuberculosis. Normal bovine serum has been used with a cer¬ 
tain degree of success in a few cases of human glanders and is 
worthy of further trial. Normal sera from other animals such 
as goats, hogs, dogs, etc., will doubtless be used just as soon as a 
pioneer therapeutist has the courage to determine their value 
in suitable cases and an individual versed in the technique of pre¬ 
paring the serum join forces. While the occasions for the use 
of normal sera are naturally somewhat limited, they are deserv¬ 
ing of more attention than they have heretofore received. 
