A Comparative Study of Central Blood Pressures in Five Amphibians

The temporal relationships of blood pressures recorded from the ventricle, conus and arterial arches are identical in Rana, Bufo and Xenopus. Pressure levels in the arterial arches are very similar in all the species. The pulse in the ventricle is large and the pressure falls to zero during diastole. Continued conus contraction after ventricular relaxation causes a divergence of pres-sure in the two chambers. Divergence between conus and arterial pressures follows as the conus relaxes. Pressure gradients between the various recording sites during forward movement of the blood is small. Theoretical considerations show that pressure-flow relationships approximate to the formula of Poiseuille. They also pro-duce no evidence for substantial pressure gradients during blood ejection. Blood pressures recorded in Salamandra are significantly lower than in the anurans. The systemic and pulmocutaneous pulses are identical, unlike the condition in anura where the pulmocutaneous pulse is almost invariably the larger. In all other respects the pressure relationships in Salamandra are identical to those in anurans.