There are disclosed various dispensing mechanisms for dispensing filamentary material through a catheter into a treatment site of a patient, for example into an aneurysm sack in a patient's vessel. In one embodiment, the dispensing assembly includes a chamber having a spherical carrier onto which filamentary material is wound. Upon injecting driving fluid into the dispensing assembly filamentary material unwinds from the spherical carrier and is pulled through the catheter to be dispensed from the distal end of the catheter. The apparatus includes a pressure sensitive valve disposed at the inlet or the outlet of the receptacle, the pressure sensitive valve being closed when the pressure of driving fluid is below a threshold and open when the pressure of driving fluid is above the threshold. The pressure sensitive valve, when open, allows fluid flow through the chamber and dispensation of filamentary material from the outlet.
