For this writer, as for the author of "On the Places in Man", the art of medicine has been wholly discovered. While for the author of "On the Places in Man" "the principles discovered in it clearly have very little need of good luck", the author of "The Art" acknowledges the practical limitations that arise in the therapeutic application of these principles. Likewise for the author of "On Regimen", the "knowledge and discernment of the nature of man in general—knowledge of its primary constituents and discernment of the components by which it is controlled" may be completely worked out, and yet in practice it is difficult to determine and apply the correct and proportionate diet and exercise to the individual patient.