. Pathogenic microörganisms; a practical manual for students, physicians, and health officers . an in others. Group Agglutination.—Many varieties of organisms have, among thedifferent protein substances composing their bodies, some that arecommon to other microbes which are more or less allied to them (). If these substances are of the. type that excite agglutinins, wehave from an animal immunized by any one of them a serum acting onother organisms somewhat in proportion to the amount of agglutinin-producing protoplasm which they have in common with the infectingorganism. These agglutin
. Pathogenic microörganisms; a practical manual for students, physicians, and health officers . an in others. Group Agglutination.—Many varieties of organisms have, among thedifferent protein substances composing their bodies, some that arecommon to other microbes which are more or less allied to them (). If these substances are of the. type that excite agglutinins, wehave from an animal immunized by any one of them a serum acting onother organisms somewhat in proportion to the amount of agglutinin-producing protoplasm which they have in common with the infectingorganism. These agglutinins, acting on substances common to othermicroorganisms which are generally but not always allied varieties arecalled, therefore, group agglutinins. Thus, in a case, the infecting para-typhoid bacilli type B were agglutinated 1 to 5700; typhoid baciUi,however, only 1 to 120, while paratyphoid baciUi type A were agglutin-ated only 1 to 10. In a case of typhoid fever an agglutination of para-typhoid type B occurred with a dilution 1 to 40, while typhoid baciUiwere agglutinated with 1 to Typhoid Bacillus Dysentery BacillusFig. 73.—Specific and common agglutinins producing protoplasm. The bacteria which are agglutinated by one and the same serum neednot at all be related in their morphological or other biological character-istics, as at first assumed. Conversely, microorganisms which, because ofthe characteristics mentioned, are regarded as entirely identical are some-times sharply differentiated by means of their agglutination. In otherwords, the groups arrived at by means of a common agglutinationhave no necessary relation to species as the term is usually employed,but only of chemical similarity. This is indicated by the diagrams inFig. 73. The letters indicate chemical substances capable of stimulatingthe production of agglutinin and of combining with it when made. Thusboth the typhoid and colon will stimulate B agglutinins and react tothem, while type A agglutinins
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