It is sometimes impossible to detect the immediate cause of an attack of sickness, even when the transition from health to disease is apparently instantaneous. Take, for example, this case. A gentleman, while quietly sitting in his counting-room, was attacked, as suddenly as if it were from a blow, with a great sense of oppression in the region of the heart, almost arresting the action of this organ, and at once prostrating his strength. No reason could be discovered why this attack should occur at that time rather than at some other. And yet there was some hidden cause, or combination of causes, which, at that moment, did its work; and we know not how long a time a preparation had been going on for this consummation, and so silently, too, as to occasion no disturbance. The physician often finds, on making his first call upon a patient, that although he may think that his attack is only a thing of to-day, there is evidence that disease must have been preying upon his system for some length of time, gradually extending its ravages, till, at length, it has made a palpable outbreak. The patient may attribute his sickness to some one cause; but there have been many causes uniting together, one after another, and swelling the still current of disease, which has now broken forth as a flood. And, as a general rule, the longer this preparation has been going on, the more obstinate does the physician expect the case will be, and the more difficulty does he find in getting a definite knowledge of the nature and extent of the malady. And if he could always trace every train of disease up to all its sources, both original and tributary, he would often be obliged to go back weeks, months, and sometimes years. In some cases, such an exploration would lead him through almost endless labyrinths. As it is, he often finds, in attempting such a search, that those facts which are the least material in the eyes of the patient, and which may be overlooked by him in giving the history of his case, reveal, far back in the distance, causes which have had more influence than any other in producing this result. A sort of cross-questioning, and that sometimes of a rigid character, is often needed, to develop material facts. The patient’s own story, without such questioning, would generally give to the physician very erroneous ideas of his case. The remarks that I have made apply with greater force to chronic than they do to acute diseases. For in them more especially, as you have already seen, does the sympathy which exists between the different organs extend and complicate the morbid condition, and the operation of unseen causes contributes, sometimes very largely, to this result.