Cats gassed with dimethylsulfate or chloropicrin in such concentration that death generally results within 4 days, usually exhibit a marked generalized analgesia, both superficial and deep.
Gassed cats react with no obvious sign of pain to operative interferences, including laparotomy and gentle friction of the parietal-peritoneum.
The analgesia develops within a few hours after gassing, and reaches its maximum in about 24 hours. With dimethylsulfate the analgesia may persist for 6 months; with chloropicrin practically normal sensitiveness has been observed 7 days after gassing.
This analgesia is considered to be caused and maintained largely by a general, low grade, tissue aspbyxia which is chiefly of pulmonic origin.