. A manual of bacteriology. Bacteriology. 132 MANUAL OF BACTERIOLOGY. property of splitting up organic compounds with the formation of various gaseous products. Perkins* has found that the power of thus breaking up sugars with the formation of gas- eous products may be lost in whole or in part by modification of environment. In some cases the power would seem to be permanently lost, in others it may be recovered again. This observation makes it necessary to interpret with great caution the results of fermentation tests as a specific means of differen- tiation between organisms which are otherw
. A manual of bacteriology. Bacteriology. 132 MANUAL OF BACTERIOLOGY. property of splitting up organic compounds with the formation of various gaseous products. Perkins* has found that the power of thus breaking up sugars with the formation of gas- eous products may be lost in whole or in part by modification of environment. In some cases the power would seem to be permanently lost, in others it may be recovered again. This observation makes it necessary to interpret with great caution the results of fermentation tests as a specific means of differen- tiation between organisms which are otherwise alike. It is important to bear this fact in mind particularly in the diagnosis of the members of the colon group. Carbon dioxide, hydrogen sulphide and nitrogen are among the better known gases that may be formed. The odors that arise from cultures and that are so characteristic of putrefactive pro- cesses depend upon the develop- ment of gases, or a mixture of gases, of considerable complexity. The bacillus aerogenes capsulatus leads sometimes to the formation of gas in the organs of the human cadaver within a short time after death. Theobald Smith intro- duced a valuable means of differentiating species of bacteria based upon their power of forming gas in media containing different sugars, or in their inability to do so. Bouillon con- taining I per cent, of dextrose (or lactose, etc.) is the culture- medium advised. The test is best conducted in a U-shaped tube, closed at one end, and at the other end provided with a bulb (Fig. 48). The tube is stoppered with cotton, sterilized ?Perkins. Journ. Inject. Dis. Vol. 4 No. i, pp. Fig. 48.— Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Williams, Herbert Upham, 1866-; Bolton, Benjamin Meade, 1857-1929. Philadelphia, P. Blakiston
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