INTERCELLULAR CEMENT AND CAPILLARY PERMEABILITY

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Abstract
This article, designed primarily to emphasize the importance of the intercellular cement in the problem of permeability, includes a discussion on the hemodynamics of the blood capillary bed. Although much has been written on permeability-changes in the capillary bed, most of the findings are largely inferential and only a few are based on direct observations of the vessels. Many of the findings are significant but, until the actual site of their action is ascertained, cannot be used for an understanding of the mechanisms involved. The fact must be appreciated that the capillary bed has a highly spe-cialized organization, the several components of which maintain a delicately adjusted functional balance between reactions of central and local origin. The dominance of a central control tends to be countered by local autonomous control. Along with this ever-shifting balance of the hemodynamics are possibilities of physicochemical changes in the composition of the several different structures which constitute the wall of a capillary. The action of specific agents on one or more of the various components, structural and chemical, requires further intensive study. Unless adequate precautions are taken and direct observational work is adhered to, it is generally impossible to differentiate between the effect of shifts in hemo-dynamic relationships, changes in functional permeability of the wall of capillaries, or actual disruptive leakages of the vessels. Most of the data in the literature deal with overall changes involving one or more of the above phenomena. Their physiologic significance with respect to the control of capillary permeability will remain obscure until the site of action of the various agencies can be detd.