He was noted for his care of his patients. 

In later years, Miss Ruby Mackay recalled a conversation between Mackenzie and a patient. 

On being told that the patient had been saddened by the death of the Duke of Clarence, Dr Mackenzie replied,"Yes, but I'm thinking about the widow down the lane." 

St James' Street, Burnley, c1890

Hill Top clearance area. 2 - 10 Malt Kiln Street, 1933. 
Privies can be seen on the left of the photgraph

His experiences in surgery led to an interest in problems of the heart and pain caused by neurological disease and he kept detailed notes about his patients' ailments.

He was always careful to use a scientific approach to his research and used more than one method to guard against error before drawing conclusions.