In your original post you have Charles Martin Brown born in 1908 so I am assuming that is wrong.
www.collectionscanada.gc.ca/databases/cef/index-e.htmlCharles Martin Brown
Reg. # 141870
b. 18/09/1883 Reading, Berkshire, England
NOK Mrs. Bessie Brown, College Hill, South Oshawa. On
occ - labourer
married
enlisted Aug 10, 1915 Niagara
Medical officer was with the 76th Battalion and his regiment number is within the numbers given to the 76th.
You can order his complete military file from the above site under "How to Consult or Order a Military File". the file will contain his movements within battalions, medical information including date of injury, field hospitals, hospitals in Britain, pay allotments, debarkation back in Canada and destination. This is your best reference to find out what happened to him during the war. It will all be in the file. I have ordered 3 files and they are amazing. Most files contain about 25 pages but some have significantly more. You have to buy the entire file but the cost is worth it. The file can be ordered through a secure online site using a credit card.
The 76th embarked for Great Britain 23 April 1916 and provided reinforcements to the Canadian Corps in the field until 6 July 1915 when its personnel were absorbed by the 36th battalion. The 36th was absorbed in January 1917 by 3rd Reserve Battalion.
I checked the War Diaries at LAC (Library and Archives Canada) and none exist for the 76th or the 36th and those that are availabel for the 3rd Reserver Battalion are for 1917 and 1918.
There is an on-line book for the 76th but Charles Martin Brown isn't on the nominal list. There are 2 reasons for this - he didn't sail with the first group to Britain or he had already transferred to another battalion in Canada. The only way to know that will be in his military file.
http://archives.org/details/historicalrecord00bigguoftHistorical Record of the 76th Overseas Battalion of the Canadian Expeditionary Force by Ernest Robert John Biggs
Bodies of servicemen were not repatriated to Canada and many were listed as dead and then missing or vice versa especially in the first years of the war. Many servicemen spent days in field hospitals before returning to hospitals in Great Britain. It is amazing that as many of them recovered as did. My grandfather spent 11 days in field hospitals before returning to Great Britain and then 3 months in hospital before returning to Canada.
Hope this helps in your research.
Val