In variations among higher forms of animal and vegetable life morphology is given a prominent part. Slight changes in form are of great importance in the unicellular organisms, and suffice to widely separate individuals; when variations can not be expressed in morphologic terms we resort to functional characteristics; it may be that morphologic distinctions exist that elude observation; it is also possible that environment may change physiologic activities without morphologic alterations.
As pointed out by Theobald Smith,1 in his paper on "Variation of Pathogenic Bacteria," read at the first meeting of the Society of American Bacteriologists at New Haven, Dec. 27, 1899, the changes in the physiologic actions of bacteria induced by modification of the culture-medium have attracted much attention because of their importance in infectious diseases. Neglect of variability has resulted in the establishment on inadequate grounds of numerous species and, on the other hand, the concession to
VARIATION AMONG PATHOGENIC BACTERIA.. JAMA. 1900;XXXIV(9):562–563. doi:10.1001/jama.1900.02460090048006