Horizontal ridges can occur as a result of severe stress, either psychological or physical, such as from infection and/or disease. . Some of these ridges are genetic -- they're inherited -- and get worse as you age.

Vertical lines can indicate poor nutrition, iron deficiency a tendency to develop arthritis.

http://www.normanallan.com/Med/askdr/finger.html

There are books on such things, but I look for only one thing in finger nails, when you cut them hopefully they are not brittle and cut nice and smooth. If they are brittle/ruff then the Calcium type herbs like Calcium Balance or better yet, the Mrs. Barefoot solution taken in good doses daily along with 3 tablespoons of sorgham and 3 tablespoons daily of lecithin/olive oil will do wonders in short time on the average.

MH