Sentence:  I cannot too strongly impress upon your mind this one foundation-principle of Autology and <WSD>Autopathy</WSD>- namely, that the essential cause or blood and flesh condition which sickens one organ or tissue, in one person, is exactly the same which sickens another organ or tissue in another person. 
Meaning of the word marked with <WSD> tags:  The philosophy that the cause of sickness in one individual is the same as the cause in another person.