In Military Cantonments, where enteric is generally more or less epidemic, it is most important that the night-soil be treated by biological methods before it be applied to the soil, as installed at most of the mills on the banks of the Hooghly, and at the East Indian Railway Workshops at Jamalpore. [Sidenote: Septic Tanks.] Of the various methods of bacteriological disposal, the closed septic tank is, for climatic reasons, the most generally suitable for India. In this the anærobic bacilli are provided with a congenial working place in the closed tank; and the ærobic ones are similarly provided for in the filter beds; the open septic tank, however, gives equally good results, as the scum, which rapidly forms on the surface, and which generally attains a considerable thickness, enables anærobic conditions to obtain in the tank itself, but care must be taken that this scum is not broken. [Sidenote: Filter Beds.] The ærobic Contact Bed filters are merely open tanks filled with coal, coke, or large cinders, through which the liquid is allowed to percolate at intervals. The bacilli live and flourish in these, and do their work during the periods from 2 to 4 hours the tanks are charged. The percolating continuous filters are those over which the effluent is continuously sprinkled and through which the fluid slowly percolates. Experiments have conclusively proved that good results can be obtained from either when a suitable sewage is applied. CHAPTER X. GENERAL SANITATION. [Sidenote: Trees and tall crops.] All the lower branches of trees in crowded areas should be pruned; these are useless or superfluous for shade, and only impede the free circulation of air. This should be done by sawing off any branch flush with the main trunk, or with its main branch. In no case should a ragged stump be left, and, if possible, the wound should be smeared with tar. Lopping must be done with a handsaw and in no case with an axe; the best season for doing this is at the end of the cold weather, but it can also be done at the end of the rains. The final form of a tree should be a straight stem up to 15 or 18 feet, without a bough, and above that height its natural shape whatever that may be. This will allow of free ventilation of the roads and streets. For the same reason no tall crops, such as Genera, or Indian corn, should be allowed near houses, and jungle should be kept cleared as far as possible. [Sidenote: Tanks.]