volume of liquor in the collecting area exceeds the amount which can be accommodated in this section it overflows at the upper edge of the intermediate wall 4 and arrives in the further section which it then likewise fills while the collecting area 3 is filling up with liquor air escapes via the overflow ventilation orifice 14 and the tubular extension through the filter 9 on the ventilation connection 8 if the maximum filling height of the collecting area is exceeded liquor emerges 10 via the overflow ventilation orifice 14 and via the conduit 13 goes past the closing bar 18 to the outlet connection 7 and from there into an adjoining drainage bag if the drainage chamber 1 has to be removed from the receptacle 21 and placed on the patient 39 s bed for example because the patient has to change beds for example it is not necessary to close the various conduits u201c by hand u201d if namely the drainage chamber 1 is removed from the receptacle 21 the projection 17 is released again and the spring 16 presses the closing bar 15 into the closed position in which it closes the inlet connection 6 and the ventilation connection 8 in that the outer wall 2 is rigid no pressure can be built up in the drainage chamber 1 even owing to accidental loading thereof which could lead to unwanted escape of liquor in spite of closed inlet 6 and ventilation 8 connections if a measurement of the liquor pressure in the patient 39 s skull is to be performed via a pressure sensor connected to the pressure measuring connection 24 in order not to adulterate this measurement the inlet connection 6 and also the ventilation connection 8 is closed the trigger 22.