There is no doubt that there is a hereditary tendency to lâtah in almost every Malay. They themselves give a very wide definition to the term, including all, from those who are absolutely automatic to suggestion, to those of a more markedly excitable temperament. Most Malays take very little notice of mild cases-- they are so common, they do not tend to become more severe, they do not, as a rule, interfere with health, and usually very little with business. There is no tendency for the condition to degenerate into insanity-- an orang lâtah (lâtah man) never becomes an orang gila (lunatic).
It has been suggested that the enervating climate of the Malay Peninsula and the archipelago is responsible for the condition. Even Europeans get 'jumpy' and intensely irritable after a few years there, and 'tropical neurasthenia', it is suggested, is the forerunner of what, in a few generations, would be lâtah. On the other hand, an almost identical affection, 'miryachit', occurs in Siberia, and 'Tourette's disease' and the 'jumping Frenchmen of Maine' will immediately occur to those acquainted with the varieties of spasmodic tic...
We come now to the question, What is the connexion, if any, between lâtah and amok? Here a recent experiment of Fletcher's may usefully be considered. Briefly it was as follows: a known lâtah in hospital was taken out of the ward into another room, where she was rendered lâtah. In the interval a dummy figure was put into the bed next hers. When she was brought back she was given a knife, and it was suggested that she should stab the apparently sleeping body. She acted on the suggestion instantly, and struck furiously at the figure. Immediately afterwards the suggestion was withdrawn, and she was horrified at her conduct. It was a correspondingly great relief, therefore, when the sheet was withdrawn and the dummy figure exposed to her eyes.
Suppose, now, that to a lâtah, consumed with a great anger or sorrow, brooding over his wrongs, such a suggestion were made, either by self-suggestion or accident. Owing to his condition, the suggestion would be stronger, more imperative, more lasting than usual. In such a case we would almost certainly get a typical amoker.
It will be obvious that the whole subject is intensely elusive. It is very difficult for the European to get behind the Oriental mind. There are almost no objective signs to go upon: the lâtah, and the amoker, except when under the influence of their affection, behaving like ordinary people, showing no stigmata of degeneracy, giving no signs of madness.
From The British Medical Journal, February 24, 1912, p. 438-9.