The effect of decerebration upon the quick component of labyrinthine nystagmus

Abstract

The effects of decerebration have been variously held to show (1) that the central cells of certain reflex mechanisms are located in certain definite regions or levels of the central nervous system. and (2) that certain other reflex mechanisms do not have their central representation in the same regions or in other regions, There has been little consistency in drawing conclusions from the results of decerebration, and frequently other considerations have entered into the matter to such an extent as to outweight the experimental results of decerebration. In addition, the experimental results as reported by various investigators are not in agreement, and one notices a lack of post-mortem reports as to the extent to which destructive hemorrhages have burrowed downward from the level of transection of the brain stem, or on other conditions which may affect the interpretation of the results. And the procedure itself is supposed to produce shock through its great trauma or not to produce shock, according to the demands of the hypothesis which is to be sustained. Sherrington's 1 statement that trauma qua trauma has little or nothing to do with the onset of shock is frequently overlooked.

The various reflex mechanisms associated with the eye have been investigated largely in decerebrated animals. Mayo 2 decerebrated a pigeon leaving the optic tubercles and the crura cerebri, and then cut below the medulla oblongata. The optic and the third nerves were left intact within the cranium. On pinching the central end of the stump of the optic nerve of one side, the iris contracted. Mayo states that contraction of the pupil could be obtained immediately after decapitation-a violent surgical procedure. The conjunctival reflex in the rabbit seems to involve the myelencephalon as well as the metelncdphalon 3 .