Still, again, the visitor may find that the symptoms are neither more serious nor less serious than he would have supposed from the dispensary interview; yet the clinical picture is different from the doctor's because the patient has thrust into the foreground of the clinical picture something which further knowledge shows to be really unimportant, while he has said almost nothing of some other feature of the trouble which is really much more serious. For example how much does the patient really eat, how does he do his work, are there complaints about him from his "boss," has he _always_ had the cough which he has only just now begun to complain of? Such questions can be better answered after visits at the home and talks with the whole family. Clearly the supplementary information thus secured by the social worker will count for nothing unless clearly explained to the doctor, and is taken up by him as part of the evidence on which he bases his diagnosis and his treatment. It is absolutely essential that the social worker should not merely make her visits and record them in her notebook, but should incorporate her findings in the medical record and deliver them not formally but effectively to the doctor's mind. Such help is needed because she can often learn far more in the quiet of an interview at home than would be possible for the doctor despite all his medical skill. For at the dispensary he questions the patient when he is confused and forgetful, alarmed, perhaps, by the sights and sounds of the clinic, and so very unlikely to give a correct and well-balanced account. _Nests of contagious disease_ So far I have been describing the work of the social worker as a process of finding out how much ails the patient and what his symptoms signify. But it is also a part of the social worker's duty to find how much disease is present not only in the individual who appears in the clinic, but in his immediate environment, to discover _nests, foci or hotbeds of disease_. In the case of a disease like smallpox, this is obvious. If a patient presented himself at a dispensary with the pustules of smallpox upon his body, it would be criminal negligence on the part of the physician not to set on foot a search of that patient's home, his industrial environment, or, in the case of a child, his school environment, for evidence that others have been exposed to the same contagion and possibly already infected. This sort of duty cannot be abandoned merely because there is no health officer at hand. It is a crying need and must be attended to at once. Now in a minor degree this is true of many other diseases as well as smallpox. We are beginning to realize that it is true of tuberculosis, so that when one case of advanced and therefore contagious tuberculosis is seen at the dispensary, machinery should automatically and invariably be set in motion to search out possible paths of contagion from that patient to others, just as if he had smallpox.