Classic Text No. 135: 'On inheritance of the insanities', by Jens Chr. Smith (1924).

Serious and realistic research into the inheritance of the psychoses started in earnest at the beginning of the twentieth century. This was encouraged by both the acceptance of the Kraepelinian classification and the rediscovery of the Mendelian model of inheritance. The application of Mendelian rules to the very complex genetics of the psychoses led to agonizing debate. The Classic Text is a translation of the introduction of the doctoral thesis of Jens Chr. Smith, a little-known Danish psychiatrist who was able to summarize, with the enthusiasm typical to his youth and with surprising accuracy, the early stages of the debate mentioned above.