The ornamental design for a medicalinstrument, as shown and described.
FIG. 1 is a front perspective view of a medical instrument according to the present invention;
FIG. 2 is a front view of the medical instrument of FIG. 1;
FIG. 3 is a rear view of the medical instrument of FIG. 1;
FIG. 4 is a left side view of the medical instrument of FIG. 1;
FIG. 5 is a right side view of the medical instrument of FIG. 1;
FIG. 6 is a top view of the medical instrument of FIG. 1; and,
FIG. 7 is a bottom view of the medical instrument of FIG. 1.
The broken lines immediately adjacent to the shaded areas depict the bounds of the claimed design, while all other broken lines are directed to environment. The broken lines form no part of the claimed design.