פירוש על קידושין 49:9

The problem with the above resolution is that there is an explicit baraita in which Rabbi teaches that if the water falls on his tongue he is pure. And there is another baraita about blemishes that disqualify a priest from serving on the altar in which Rabbi agrees that even if only part of his tongue was removed, he cannot serve. Clearly, Rabbi considers the tongue an external part of the body.