Linda, not really IOM an issue; and not sure if this is related, but there is a death registration for Wentworth Ont. for a John McGlennan, Feb 13th 1880, age 67 ( born about 1813) in the Ontario 1869-1936 death records. Also have you been on Ancestry.ca there are some threads (2004) also related to John McGlennon of Lakeport.

There is a John McGlennon, age 63 (from Northumberland, Ont) included in a list of insane asylum inmates for upper Canada. No date is provided, but the private database spans 1841 - 1891.