In muscular rheumatism, neuralgia, neuritis, or in case of a local boil or abscess indicating local disturbance of the trophic influence of nerves, clear and definite tracings are common. Muscular spasm, such as wry-neck, usually has a very tender nerve associated. Localized painful disease of any kind is likely to be associated with a very definite nerve tenderness, as is the case frequently with appendicitis, ovaritis, hepatic colic, etc. The painless disorders, or various disorders of spleen, diaphragm, heart, lungs, etc., though they be of a very serious nature, seldom are discoverable by nerve-tracing unless their serous membranes are involved. Tracings _may_ be made from D 2 or 3 to anterior thoracic walls in heart or lung disease but are not common. Any spinal nerve may be traceable at times through at least a part of its course. Sources of Error Several of these have been mentioned, such as the natural suggestibility of both examiner and patient. Among others are: failure in the back, thigh, or leg to reach the really tender nerve because of the interposition of several muscle layers between it and the finger, ignorance of nerve-paths, failure to apply equal pressure to all parts of a nerve, application of such heavy pressure that muscle tissue is bruised and hurt, and failure of full co-operation on the part of the patient. Let us consider these in turn. If several muscle layers interpose themselves between the searching finger and the nerve, it is proper to push aside the intervening layers, using a twisting and rolling movement until the finger feels _underneath_ the muscles. This done, and a tender nerve found underneath several muscle layers, the same amount of overlying tissue must be pushed aside each time the finger searches for the nerve. Only exhaustive study of the anatomy of the typical nervous system will enable the examiner to know exactly at what point a nerve will become more or less superficial. Unless he does know this it is best to follow the neutral rule that nerves tend to follow the long axes of ribs and limbs and to maintain their depth beneath the surface throughout their course. This statement is too general for accuracy. Care should be taken that equal pressure be made on all points palpated on one nerve. If the nerve pass over a bone, _less force_ is needed to exert the same pressure than if it overlie muscle or other soft structure. The force used varies constantly as the hand moves from place to place, according to the density and hardness of the structures overlying and underlying a nerve. Sufficiently heavy pressure will elicit tenderness in all except anaesthetic patients. But if a nerve be irritated it will be tender without heavy pressure, when the finger really makes a close contact with it.