C.—Action on Centres of Cranial Nerves.
Among the symptoms denoting paresis of motor-centres of cranial nerves, together with sympathetic ganglia, the first and most noteworthy is the early dilatation of the pupil. This truly pathognomic condition is never absent, and becomes intense when paresis becomes intensified into paralysis. The most glaring light, in immediate proximity to the eyeball, has then no effect whatever on the pupil. If it remains dilated after strychnine injections have restored consciousness and the power to walk, it is a sure sign that the snake-poison is not completely counteracted, and will in all probability re-assert itself, necessitating another injection, whilst a pupil restored to its normal condition justifies the conclusion that the patient is safe.
Another symptom denoting paresis of the cranial nerve-centres is a marked change in the expression of the face. The features become relaxed, and lose their mimetic play. The cornea is dull, and, together with the anterior surface of the eyeball, becomes dry, as the eyelids are moved imperfectly, if at all, and the tears in consequence are not properly distributed over the conjunctiva. The nostrils become more or less immovable, and the naso-labial fold is obliterated, whilst the lower lip hangs down. The lips are apart, as the lower jaw is not held up by the muscles. When paralysis supervenes it drops entirely, and the tongue protrudes.
Deglutition, somewhat difficult in paresis, is completely suspended in the paralytic stage, through paralysis of the soft palate, the pharynx, and œsophagus. Liquids forced on the patient in this extremity may partly flow down the œsophagus, but will also enter the larynx, and their administration should be carefully avoided.