Sentence:  Medical materialism seems indeed a good appellation for the too simple-minded system of thought which we are considering. ... All such mental over-tensions, it says, are, when you come to the bottom of the matter, mere affairs of <WSD>diathesis</WSD> (auto-intoxications most probably), due to the perverted action of various glands which physiology will yet discover. 
Meaning of the word marked with <WSD> tags:  A hereditary or constitutional predisposition to a disease or other disorder.