of the overheated exhaust gas from the catalyst 10 which still has energy rich constituents as a result of incomplete conversion is prevented at the inlet opening 13 arranged laterally at a distance from the catalyst 10 are bypass holes 25 in the dividing wall 24 through which the exhaust gas can flow from the first space 26 into the second space 27 the partial streams which flow through the bypass holes 25 are not converted by the catalyst 10 in the second space 27 the exhaust gases which flow from the catalyst 10 and from the bypass holes 25 are thoroughly mixed as in the exemplary embodiment according to fig5 the exhaust gas located behind the catalyst 10 is cooled by the cold untreated exhaust gas which enters into the second space 27 through the bypass holes 25 the exhaust muffler 100 can have an insulating layer not shown which is preferably arranged on the housing wall 12 it is hereby achieved that the temperature of the housing 12 is kept as low as possible aluminum silicate which is a poor heat conductor can be used as insulating material for example however other materials with similar insulating properties can also be used a double walled design is also possible it will be appreciated by those skilled in the art that.