With all such commotions, the most striking events of the world are in intimate relation, and unquestionably, amid the changing forms of existence in the human race, more has always depended on the prevailing tone of thought than on the rude powers by which those events were produced. The historian, therefore, who would investigate the hidden influence of mind, cannot dispense with medical research. The facts themselves convince him of the organic union of the corporeal and the spiritual in all human affairs, and consequently of the innate vital connexion of all human knowledge. Hence, in a medical point of view, how vast is the field for observation presented by the history of popular diseases. Present bodily sufferings[348], are, collectively, but a step in the development,—but one phase of morbid life amid a long series of phenomena, and hence are not fully understood without a previous knowledge of the past, and historical research. How can we recognise the ring of Saturn as such, so long as our axis of vision is in its plane, and we see it only as a line. Great pestilences have vanished or been dispersed; from causes apparently the most insignificant, the most important consequences have resulted, and throughout the vicissitudes of danger and devastation, the operations of mighty laws of nature are everywhere manifested in the social tendencies of entire centuries. This is no aërial realm of transitory conjectures—facts themselves speak in a thousand reminiscences. If we do but investigate the past with unprejudiced assiduity—if we do but consider even the few successful researches which have hitherto been made in historical pathology, (perhaps those who are kindly disposed will recognise even mine,) we shall not fail to arrive at a centre of reality, which the healing art, to its great detriment, has hitherto been far from reaching, whilst it has occasionally penetrated into a less fertile soil, or even encumbered itself with the accumulated rubbish of the pedantic dogmas of the schools.