The solvent for dissolving the lactic acid polymer of higher molecular weight may advantageously be that capable of dissolving this polymer in an amount of 10-fold by weight or less of the lactic acid polymer, and specifically, halogenated hydrocarbons such as for example chloroform, dichloromethane and the like, aromatic hydrocarbons such as for example toluene, o-xylene, m-xylene, p-xylene and t