1. The transport of the lead cation has been investigated using the everted sac preparation of Wilson & Wiseman (1954).2. Only a small percentage of lead was transported into the serosal compartment but there was a rapid and massive uptake onto the tissue. There was no significant difference in the amount of lead cations transported across different regions of the small intestine.3. Both the rate of transport into the serosal compartment and the tissue uptake increased linearly with increasing concentration of the lead cation, from 10-7 M to 5 × 10-5 M. Little evidence for saturation of serosal transport or tissue uptake was found.4. Lead transport into the serosal compartment appeared to be related to water movement, but was little affected by changes in glucose concentration and temperature.5. It is concluded that lead is transported into the serosal space by a process of passive diffusion linked to water transport.6. The interaction between lead ions and the intestinal tissue was extremely tenacious and displayed characteristics of covalent bonding.7. It is suggested that the lead cation interacts with tissue phosphate ions thus removing lead ions from the transport pool. Chelation of lead to form a neutral species reduces this interaction and also promotes transport.
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