Never had a 7th series apart but if the design is similar to the somewhat later (32-39) senior transmissions you'll find a a round ball intergrally forged as part of the cane which nests into a socket in the housing, a cross pin which allows the up/down and left/motion (pictured below) with a smaller spring which lets the cane come to rest in the right-hand side of the pattern, and a large conical spring and retainer. The end of the cane has a enlarged section which engages the shifter rails. A very simple construction, there is a good picture in the 1933-36 parts manual, pages 176-177; again I'm assuming the 7th series to be similar. Also a picture in the 35-49 Motor's Manual which I'll scan for you in a few moments.