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Red cells arrested by fine fibers and subjected to drag forces in a moving stream of fluid can be stressed beyond the point of rupture. The technique, which is basically an in vitro analogue of the microangiopathic hemolytic state, thus permits a study of red cell behavior over the entire range of stress that the membrane can withstand. Measurements made by this approach show an exponential relationship between the velocity of fluid flow and the resultant membrane deformation. Such exponential membrane deformation is consistent with the morphology of red cell fragments and appears to explain their mechanism of formation.

Red cells moving in a stream of fluid can be arrested by means of a network of fibrin threads. Those cells which fold over a fibrin thread present to view a flat strap-like portion of membrane in which the strain can be easily observed and accurately measured both optically and by scanning electron microscopy. Preliminary results obtained by this method show elastic strains of nearly 300% and indicate that the stress required to produce these large strains is an order of magnitude greater than that reported by other methods.

The zeta sedimentation ratio (ZSR) is a measurement similar to the determination of the erythrocyte sedimentation rate (ESR) but possesses sevaral advantages. It is unaffected by anemia and responds in a linear manner to increase in fibrinogen and/or gamma globulin. The normal range is identical for males and females. A blood sample, contained within a vertically oriented capillary tube, is subjected to four cycles of dispersion and compaction. At the conclusion of this process, the hematocrit of the blood in the red cell-containing portion of the capillary tube is measured. This hematocrit, a measure of the closeness with which red cells will approach each other under a standardized stress, is the ZSR.

A large number of red cell volume distribution curves can be generated on the same sample of blood by manipulating the length of the Coulter Counter aperture and the shape of the red cell. Curves derived from sphered red cells flowing through an aperture 70 x 98µ long, or longer appear to be relatively free from artefacts and therefore the most likely to be "real." The use of long apertures to size sphered red cells will give a volume distribution curve that is approximately Gaussian and with a mean that is large relative to the variance. Whether red cells are Gaussian or log normal in their volume distribution is very difficult to determine. On a particle population where volumes are controlled as closely as on red cells (i.e. with such a low variance), the normal and the log normal distributions become practically indistinguishable. If in the future this decision can be reached by some independent means, then the volume distributions using the Coulter volume transducer can be easily and simply fitted to the shape desired by appropriate manipulation of aperture length. These ideal volume distribution curves are not likely to differ markedly from those obtained under the conditions suggested in this paper. For the present, use of a 70 x 98µ aperture to size red cells sphered by suspension in isotonic Sodium Potassium Tartrate will contribute to considerably greater accuracy in identification of red cell subpopulations in abnormal blood.

The relationship between intravascular coagulation and schistocyte formation has been adequately documented in animal experiments and in in vitro models. A case report is presented of a patient who suffered from micro-angiopathic hemolytic anemia during life as a result of disseminated gastric adenocarcinoma. The fibrin microclots found in his vasculature on postmortem examination indicate that in intravascular coagulation, both in the human and in the experimental animal, fibrin initially polymerizes in the form of fine fibrin strands. These strands, the main etiologic factor in producing schistocytes, are constantly being lysed or rendered amorphous, and rarely persist in postmortem tissues except under unusually favorable conditions. Postmortem histologic study of one case where such favorable conditions did exist indicates the essential identity of the pathologic process in man and in experimental animals.

New evidence is presented to show that the dimple and the annulus of the red cell are not restricted to specific locations on the membrane. This eliminates all but one of the current theories of biconcavity and supports the view that the membrane has unusual mechanical properties such that, although it cannot support surface shear, it can resist both bending and increase in total surface area. The feasibility of such a material is demonstrated by means of a macromodel. The model represents a class of structure that until recently has received little attention but that strongly suggests long-range protein interaction in the membrane surface.

Negative staining of whole mounts of platelets preserves several structures not previously described. External to the plasma membrane there is a coat which contains electron dense bodies of varying shape. External to the coat is a region which stains intensely with phosphotungstate. Platelet granules coexist with tubules in the granulomere as well as with a large number of other membraneous structures. A speculative interpretation of the function served by these structures in platelet physiology is proposed. The PTA halo denotes a cloud of adsorbed plasma proteins, including fibrinogen maintained in the platelet environment by the coat. During viscous metamorphosis, coagulation is catalyzed by discharge of the contents of the granules and shedding of the coat.