When the Nails appear very flat and sunk into the flesh at the base they denote nerve diseases.

When they are "ribbed" across the Nail from side to side, the danger is still more apparent.
When a deep furrow is found across the Nail, it is a sign in any hand that an unusual call has recently been made on the nervous system by illness.

If the following rule be studied, the date of this illness or strain can be very clearly indicated.
As it takes about nine months for a nail to grow out from the base to the outer edge, the nail can easily be divided into sections.

When the furrow or very deep "rib" is seen close to the edge, the illness took place about nine months ago; when the furrow is seen about the centre, the date was about from four to five months, and when at the base, about one month previously.
White spots on the Nails are a sign of general delicacy, and when the Nail is seen covered with small white flecks, the whole nervous system is in a low state of health.
LONG NARROW NAILS Very narrow Nails (Plate V., Part II.), show spinal weakness, and when extremely curved and very thin they indicate curvature of the spine and great delicacy of the constitution.
FLAT NAILS When the Nails appear very flat and inclined to lift themselves up from the flesh towards their outer edge, the threatened danger is towards paralysis, and still more so when they look like a shell and are pointed towards the base (Plate V., Part II.).

When these Nails are without any signs of moons, and whitish or bluish in colour, the disease is in a very advanced stage.
THE MOONS OF THE NAILS Large "Moons" always denote strong action of the heart and rapid circulation of the blood, but when unusually large they indicate too much pressure on the heart, rapidity in its beat, the valves over-strained and danger of bursting some blood vessel in the heart or in the brain.
Small "Moons" indicate the reverse of this; they always denote poor circulation, weak action of the heart and anaemia of the brain.
When close to death the "Moons" are the first to take on a bluish look, and later on the entire Nail becomes blue or almost black in colour..