tokens: The 65 dogs in the study received injections in the subarachnoid space as follows : 6 to 8 ml of bupivacaine ( N = 15 ) , 2 - chloroprocaine - CE ( N = 20 ) , low pH normal saline ( pH 3 . 0 ) ( N = 20 ) , or normal saline ( N = 10 ) .