The structure of the dwellings of the labouring classes; the nature and extent of their internal accommodation, and of the means for securing cleanliness, for removing filth, for promoting ventilation, and for providing warmth with due economy, can be most easily ascertained by medical gentlemen who devote their time to the frequently gratuitous services of public institutions; they also are most competent to discriminate between the direct influence of the habits of the poorer classes, and of the external circumstances by which they are surrounded, on their sanitary condition; while on the other hand they will not be liable to fall into the error of supposing that these habits are independent of arrangements which administer to domestic comfort.
The Commissioners trust, therefore, they may rely with confidence on your affording them your valuable assistance in the inquiry which they are directed to pursue. They trust you will permit them to suggest that if the cases recorded in the books of your hospital were grouped according to the districts from which the patients were removed, you would at once be able to define in a map those parts of your town most subject to contagious febrile diseases, and to furnish the Commissioners with the number of cases of each febrile disease occurring in each of these districts, and would possess the means of ascertaining and delineating the features of those districts in all that relates to the sanitary condition of the inhabitants, and to medical police. Besides the general influences alluded to in the former part of this letter, you will probably find it useful to ascertain whether any injurious consequences are clearly attributable to certain classes of manufactories surrounded by the habitations of the poor, to the location of slaughter-houses, tanneries, ancient burial grounds, &c., amidst dense masses of the population.
In the course of this inquiry it may be found necessary to distinguish the extent of disease caused by physical or removable agencies, by malaria created by defective drainage, or the bad construction of the dwellings of the labouring classes, from disease caused by destitution of the proper means of subsistence arising from poverty. It may be expected of the medical practitioners from whom the Commissioners hope to obtain reports, that they will make the distinction wherever it is found to exist.