INTRODUCTION
This paper is presented as an experimental inquiry into the cause of the severe shock which sometimes follows the injection of serum into the subarachnoid space of the spinal cord. The sole object of this investigation has been to determine the mechanical effect on the spinal and medullary centers, of increasing the amount and pressure of fluid in the spinal subarachnoid space. For this purpose Ringer's solution has been used, as this contains the different inorganic salts of a real physiological salt solution, and is therefore preferable to the isotonic solution of sodium chlorid commonly called by that name.No attempt has been made to use serum in any of these experiments, as it was desired to separate the mechanical effect from the obscure symptoms of serum-sickness sometimes produced by injecting a foreign blood-serum. For this reason Ringer's solution was selected, as it contains only the