(from page 120)
GREAT DEFENDER Co.10
Co.10 (Colon 10) is named Arm Three Mile and nicknamed GREAT DEFENDER. The Chinese name, Arm Three Mile, suggests that this acupoint is used to strengthen the body as is Leg Three Mile ZUSANLI (St.36 explained on page 114). Like St.36, Co.10 is located three body inches from a bony prominence near the elbow (lateral epicondyle of the humerus).
The GREAT DEFENDER (Co.10) is a good acupoint for increasing the body’s defensive energy. The immune system will let you know when it is fighting disease because this acupoint becomes sore (ahshi). It is an amazing early warning system.
The day before the onset of
symptoms, this point announces, by means of increased tenderness, that the
immune system has detected an invader. If you do not take it easy and do
not take supplements to boost your immune system, you will likely suffer
from a cold or flu. See for yourself, test this point everyday. 
Co.10 is four fingers from the bony bump outside the elbow toward the thumb. To find this point on yourself, place your left hand on the right side of your navel, while lightly grasping the forearm with the right hand.
With your right thumb, stroke (TUI) the thick muscles on top of the forearm, near the elbow. If you rub (AN) along the line from the elbow toward the thumb, you will feel muscles separate into two groups, then you can feel the bone under the thick muscles.
You will find a spot that is more tender than other spots along the bone between the two groups of muscles. Rub this point on yourself every day so that when its sensitivity changes you will know your immune system is active.
To locate on a partner lying face up, place their hand on their abdomen and follow the directions above. You can also leave their arm by their side but the hand must be palm upward.
To locate on a partner lying face down, lift the arm by the elbow and place the hand above the head, with the arm bent. With your partner’s hand held so that the thumb is up, feel for a separation on top of the forearm in the thick muscles near the elbow.
NOTE: Some people have a line parallel to the elbow crease where this acupoint is located. Remember to hold the hand so the thumb is on top.
Whether you are finding this point on yourself or a partner, the bones of the arm must not be crossed or the point will be hidden under a large muscle. Notice if you hold your arm in front of you palm up, the bones of the arm (radius and ulna) are uncrossed. You can feel the difference when you turn your palm down; the bones cross.
In all the above positions, the bones of the forearm (radius and ulna) are uncrossed. This places the spot on the bone below the muscle separations. Now when the muscles separate into two groups, you can stroke the bone directly under your fingers to find the spot. If the bones are crossed, the most tender spot on the bone will not be easy to find.
Measure four fingers toward the thumb from the bony bump near the elbow, feeling for a small knot above the bone. If that is the most tender spot, the immune system is active. Remember the hand and arm must be in the correct position to locate this point. The acupoint will be lined up directly beneath the separation in the muscle groups, so you can easily press Co.10.
Key concepts to remember about Co.10:
 | Location: In a separation between the forearm muscles, four fingers width from the bony bump near the elbow, toward the thumb |
| To find: Stroke along the muscle separation. Feel for a small knot next to the bone where the muscles separate |
| Deqi: Toward the hand and/or up the arm |
| Use: Improve resistance to disease. Strengthen the arms |
| Pain: Head, neck, low back (especially pain and stiffness in the arm) |
| Condition: Stomach complaints, diarrhea, hypertension |