In the condition referred to in the foregoing remarks the rigidity is so complete that there is little probability of any mistake occurring. There is, however, a form of persistent rigidity which, although only apparent, is at first sight so absolute that unless an examination of the right kind be made, errors in diagnosis are more than probable. This form of rigidity is due to muscular contraction or spasm, and is most frequently met with in muscular rheumatism, hysteria, neuro-mimesis, and as a consequence of reflex irritation (vide table), and so complete sometimes is the fixation of the vertebrae that a condition of absolute rigidity is produced. Bearing in mind the essential factor - muscular contraction - in these cases, it is obvious that any method of examination of a rigid spine should be made with a view to eliminate the question of deception from this condition.

Excepting cases of inflammation, congenital abnormality, or central nervous disease, it will be found that when stiffness of a joint, vertebral or otherwise, is due to muscular spasm, relaxation of the muscles concerned for a longer or shorter period is merely a question of putting strain upon them for a sufficiently long time. The relaxation may be only momentary, but it will come, and however short the term of relaxation may be, it is sufficient to provide the key to the situation.

The administration of an anaesthetic would, of course, at once settle the question of the relation of muscular spasm to the rigidity; but it should be borne in mind that the anaesthetic, although it may set at rest the question of rigidity, often veils, for the time being, other symptoms of importance. Moreover, the administration of an anaesthetic unnecessarily is not to be commended. In the examination to determine the points under discussion, all that is necessary is that the patient, stripped to the hips, standing with the back to the observer, should bend forward in the usual way, the lower limbs being kept extended at the knee; the hand of the observer at the same time resting upon the rigid portion of the spine. The bending forward of the trunk having been carried out as far as possible, the patient should not immediately begin to resume the upright position, as is usually done in the examination of spinal cases, but should maintain the bent position for a considerable period, at all events for two or three minutes. It will then be found that if the rigidity is due to muscular action, a slight quivering of the muscles lying under the hand of the investigator will occur; this quiver will, if the bent position be still maintained, be replaced by a series of jerks (stammering), until in some cases the flexibility of the vertebral column can be freely established. In infants and the very young this method is obviously impracticable, but in such the same end is attained by resorting to the only delicate test of spinal rigidity available - namely, by placing the small patient flat on the back and lifting it off the couch or bed by one hand placed beneath the spine; when held up in this way for a minute or so, if the rigidity is due to muscular causes, the result mentioned will follow. So far as I know, this method of testing the rigidity or flexibility of the spine of infants or very young children is the only truly reliable one. The method of placing the child in the prone position and moving its lower limbs and pelvis from side to side is far less sensitive. I know of no more important point in the diagnosis of rigidity of the spine than that afforded by the 'stammering spine,' and it is a point which may altogether escape notice if the patient, whilst being examined, is allowed, after bending in the orthodox manner, to resume the erect position immediately.