1. A rotary drill rod comprising an elongated pipe having a longitudinally extending bore therethrough and an annular bit at the distal end thereof, the proximal end portion of the bore being adapted to slidably receive a piston-like means therein, but there being an annular shoulder about the periphery of the bore at the terminus of said portion to engage the means in the rod adjacent the bit, and means defining an annular seat about the periphery of the bore between the shoulder and the mouth of the bit, which is of lesser inside diameter than that of the shoulder, to engage an elongated member which is slidably inserted into the distal end portion of the bore through the opening of the shoulder when the piston-like means is engaged with the shoulder, the distal end portion of the bore having substantially the same diameter as the opening in the shoulder, but there being fluting in the peripheral wall of the bore, which extends generally longitudinally thereof between a point adjacent the shoulder and a point about the periphery of the seat, and porting in the body of the bit, which extends generally axially thereof between the fluting and the working face of the bit at the distal end thereof, to form a passage about the member through which fluid can be released into the working face of the bit from a point adjacent the opposite end of the member, said bit having a greater diameter than the pipe and being adapted so that the released fluid can discharge from the face of the bit toward the proximal end of the pipe on the opposite side of the pipe from the member.