These three papers have developed the following facts, which suffice to explain completely the anemia of lead poisoning.

In vitro, the exposure to a very small amount of lead greatly changes the surface of the red blood cells. Their permeability to water is so altered that they shrink and are incapable of swelling as much as normal cells. With this is associated a marked increase in the resistance to different osmotic surroundings—demonstrated by far less hemolysis than normal in salt solution of very low concentrations. The "leaded" cells, however, are relatively short lived, and hemolyze readily as the result of slight trauma. These observations can also be demonstrated in vivo as experiments with rabbits with acute lead poisoning show. In addition to these effects on permeability, lead alters the physical properties of red blood cells so that they lose their normal stickiness and are no longer agglutinated by the sera of different isoagglutinating groups. All these changes are evidence of an effect on the surface of the cell; the interior of the cell does not undergo disturbances; at least, the physiological properties of the hemoglobin remain normal. The chemical reaction which causes these physical changes in the cell is a precipitation of insoluble lead phosphate and a formation of acid. This causes the "leaded" red blood cell to change from an elastic distensible sac, to one which is contracted, relatively inelastic and brittle. In such condition the cell can poorly withstand the trauma involved in circulation of the blood, and this lack of resistance probably explains the marked destruction of peripheral blood in lead poisoning.

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