Abstract: The placental pulps notably of human origin are separated from the placental blood, which is removed, and the pulps are macerated in a solution at a pH comprised between 5 and 10, e.g. isotonic NaCl solution, preferably at neutral pH, in the presence of an amino-acid inhibitor of plasminogen activation, at a molar concentration comprised between about 0.001 and 0.1 M, preferably of the order of 0.035 M. The pulps are removed and the solution containing the compounds of the plasminogen type is recovered. Preferred inhibitors are L-lysine, epsilon aminocaproic acid, and trans-4 aminomethyl cyclohexane carboxylic acid.