Abstract
Objectives : Contemporary researches suspect that, contrary to the past belief, the understanding that the cause of warm pathogen lies in the upper portion of human body is an understanding that had been well-established even before Yetianshi. This new understanding now requires us to contemplate the process of theoretical development which this understanding, termed Onsasangsu, had taken within the boundary of the theory of warm pathogen. This paper aims to shed light on this within the framework that this is the emergence of a new theory of warm pathogen caused by a new understanding of warm pathogen. Methods : First, the theories of warm pathogen as developed by historical doctors were studied, and elements that seem to be related to the understanding of Onsasangsu were selected and studied to understand their theoretical characteristics. Furthermore, the paper studied what academic significance do these theories have on the development of the theory of warm pathogen. Results & Conclusions : Provided that the underlying assumption of Onsasangsu is that febrile diseases are caused through moutn and nose, the study showed that this understanding arose before the period of Qing Dynsasty from the need by many doctors to differentiate the pathogens of various diseases such as the disease of heat, febrile disease, and epidemic. The reason that these discussions could not have much impact on the study of febrile disease during the Qing Dynasty could be because they were not passed on down to the future generations, or because commonly held perspective was unable to accept criticisms.