1. The microbic-tissue affinity of an organ or group of tissues may be expressed as the average percentage of microörganisms deposited in these tissues per passage of a perfusion fluid.

  2. The microbic-tissue affinity varies with the organ or group of tissues tested. Thus, the central nervous system shows a microbic affinity of 0.5 per cent, the spleen a microbic affinity varying from 20 per cent to 60 per cent, and the liver a microbic affinity varying from 4 per cent to 80 per cent, depending upon the microörganisms tested. The remaining extra-hepatic tissues show affinities varying from 4 per cent to 6 per cent.

  3. The microbic-hepatic affinity is increased by immunization. The immune liver shows an affinity of at least 80 per cent for all microörganisms thus far tested.

  4. This increased hepatic affinity is due to the action of specific endothelial opsonins.

  5. The endothelial opsonins also increase the microbic-splenic affinity. So far as tested, however, they are inoperative with the other extra-hepatic tissues.


Presented before the American Association of Pathologists and Bacteriologists, Washington, D. C., May 2, 1922.

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