The ornamental design for a medicalinstrument, as shown and described.
FIG. 1 is a left side view of a medical instrument according to the present invention;
FIG. 2 is a right side view of the medical instrument of FIG. 1;
FIG. 3 is a rear, bottom, left side perspective view of the medical instrument of FIG. 1;
FIG. 4 is a bottom, right side view of the medical instrument of FIG. 1;
FIG. 5 is a front, left side perspective view of the medical instrument of FIG. 1; and,
FIG. 6 is a top, right side view of the medical instrument of FIG. 1.
The dashed lines illustrate environment that does not form a part of the present invention, and no claim is made to the material illustrated with dashed lines.