side parts of each curved section 18 of one jaw press against the corresponding side part of the other curved section 18 they thus form together a steady ring which will delimitate the operating field each curved section 18 is provided at both lateral sides with sheaths 20 as represented at fig6 the corresponding sheaths 20 of each curved section 18 lie at this moment i e when the rib retractor is in working shape parallel to each other to reinforce the stability of this ring u form securing bridges 22 are then inserted into the adjoining sheaths 20 the curved sections 18 forming now a mechanically continuous ring the handles 6 fastened to the jaws by known mortice and tenon joint means 21 can be removed see fig7 it will be noted that the slight curvature of the handles 6 not only allow them to match the curvature of the curved section 18 of the jaws but also contributes to ensures their mechanical strength an advantage of the present retractor 1 over prior art devices is that the surgeon can estimate from the effort he has to exert on the handles 6 the stress the ribs 14 undergo when pulled apart fig8 and 9 are artist 39 s views of the fastened jaws seen from various points of view the securing bridges 22 comprise support means 24 for securing possible other medical devices as catheters sucking tubes suturing wires the support means acting then as suture organizers an apparatus as described in wo 2006 000514 and so on fig1 and 11 display an advantageous additional feature 25 that can be used with the retractor 1 of the invention if the surgeon is of opinion that the ribs 14 should be moved further apart.