Hope these help:
This should take you to a digitized copy of his death certificate:http://haldigitalcollections.cdmhost.com/seeking_michigan/se...
This is from a book you can access through Google Books:
History of Ionia County, Michigan By Elam E. Branch pg 429
"IONIA'S PIONEER DOCTORS.
The following excerpts are from an interesting paper read by Dr. C. S. Cope before the Ionia County Medical Society on Thursday evening. October 17, 1907, and are considered worthy of preservation:
The year 1907 has witnessed the passing of two of Ionia county's oldest physicians, Dr. William B. Thomas and Dr. Henry Tremayne. For more than forty years they rode the hills and valleys in and about Ionia and had, after a long and arduous contest with those things that beset the life of the county physician, passed onward to their reward.
Like a shock of corn fully ripe, each was garnered by the stroke of that scythe whose edge is ever keen. Not far apart in Highland Park, they lie in dreamless sleep, while pressing closely to each casket's lid affection's precious roses guard well the doctor's rest."