A Technique for the Perfusion of Laboratory Animals for the Recovery of Schistosomes

The search for and the recovery of schistosomes from laboratory animals presents a problem if the total number of worms in the animal must be ascertained, or if comparative figures must be compiled on the number of worms present in the blood vessels of various organs and regions. The most important area involved is the mesenteric-portal system, but worms may also be present, especially during their migration, in the pulmonary and systemic circulations. Inspection of the mesenteric veins and main portal vein, and manual dissection or comminution of the liver are not likely to reveal all of the worms, especially the small ones, and the time consumed in removing them individually is considerable. A search for worms early in the infection would be impossible by this technique. A desirable method is one which will standardize the individual differences of the operators, effect a reliable removal of worms, and be applicable to early infections. A modification of the perfusion technique of Faust and Meleney (1924) serves these purposes. The principle of this technique is to isolate the organs and regions to be examined and to perfuse the vessels in which the worms may be present from their smallest to their largest branches. They accomplished this in the case of the mesenteric system and the extremities by perfusing from artery to vein, in the case of the liver by perfusing from hepatic vein to the portal vein, and in the case of the lungs by perfusing from artery to vein. Improvements of the technique, made in this laboratory, include supplying a continuous flow of the perfusing fluid, arranging the apparatus in such a way that several animals may be perfused simultaneously, and adding details to obtain more complete collection of worms.