Yesterday a very fine horse, belonging to the prison van for Tothill-fields, was discovered to be insane. It appears that about a month ago a large Newfoundland dog strayed by chance into the stables where the prison vans' horses are kept, or put up, in Drury-lane, and was permitted to sleep along with them, though at times he betrayed signs of snappishness, and had bitten two or three persons who frequented the livery-yard. Something strange was remarked in one of the horses when putting him into the stables on Tuesday night, where he plunged, and pawed much with his fore feet. The very next morning, on going to the stable to prepare the animals for his daily task, he was found foaming at the mouth, grinding his teeth, and pawing violently, when a knacker was sent for, but it was impossible to attack him with the pole-axe in the usual way. Throwing a rope about his neck, he was at length chained up to a post, by which precaution his throat was effectually cut, though he was worth 25£ at least; and it is now conjectured that this fine animal must have been bitten by the Newfoundland dog before mentioned, which has disappeared.