Studies have been performed on changes in the activity of hydrolytic enzymes in spinal cord following a toxic action of calomel. With the use of a gastric cannule, the rats were being administered mercurous chloride. The first group were given Hg2Cl2 in a 0-05 g. dose for four days whereas the second experimental group received a 0-012 g. for ten days. As a result of the studies, both in an acute and subacute calomel intoxication, an increase in TTP-ase and NsE activity in spinal cord as well as a decrease in ATP-ase, AChE and AcP activity were found. It was also shown that mercurous chloride intoxication exerts of influence on AIP and BuTJ activity. In the discussion an attempt was made to explain some of the observed phenomena.