Abstract
The net fluxes of water, sodium, and chloride were measured in vivo by perfusion of the jejunum. There was a net absorption of these three substances from isotonic saline solutions in normal rats, but a net influx to the lumen in each instance in rats infested with the nematode Nippo8trongylu8 muri8. The unidirectional fluxes of sodium and the net fluxes during perfusion with hypo- and hypertonic saline solutions indicated that this was fundamentally due to a derangement of efflux while influx was unaffected. The gross effect, however, was also due to an increase of influx because of the greater weight of mucosal tissue per centimetre of jejunum in the infested animal. The unidirectional fluxes of water did not support these conclusions unequivocally. The fluid which accumulates in the infested� small intestine can be explained by these results.