A medical apparatus for injecting or withdrawing biological or therapeutic fluid includes a syringe body defining a syringe cavity into which fluids can be introduced or withdrawn by way of a fluid port and a vacuum port. A piston is positioned for reversible movement in the syringe cavity between the...http://www.google.es/patents/US5176642?utm_source=gb-gplus-sharePatente US5176642 - Vacuum powdered syringe
