All the work at Havana was done by men trained and instructed as to the life habits of the mosquito, and the same was the case for the first three years at Panama, when the effective mosquito work was done. Whenever speaking or writing on this subject I have insisted upon the necessity of having the execution of the work in the hands of men who have been trained in anti-malarial procedure. Another duty of the inspector was to see that the houses were properly screened, and that the screens were kept in effective condition. The Commission had several thousand buildings scattered in thirty or more towns, and it endeavored to keep all these buildings mosquito-proof with wire netting. Mr. Wright, the architect of the Commission, developed several very useful types of houses, well adapted to a tropical country and for the use of wire netting. The general plan was not to attempt to screen the doors and windows; such screening is more or less imperfect, and with several entrances to a house, it is impossible with any ordinary care to prevent the doors being left open. Mr. Wright therefore planned his houses so that they were screened in, having only one door of entrance. A house screened in this way is very thoroughly protected against the mosquito. The housekeeper, with very little attention, can keep closed the one screen door that gives entrance to the house. Another great advantage of such screening is that there is very little interference with the circulation of the air. We used a wire netting of sixteen strands to the inch. In the case of a window screened with such wire, a large part of the air that would ordinarily enter is kept out, and the interior of the house is made hot and uncomfortable in a warm climate. With the whole side of the veranda screened the amount of air kept out is not appreciable, and at Panama there was no complaint that the screening interfered with the ventilation. Another very great advantage of this style of building was that the galleries could be used as living- and sleeping-rooms, and this at Panama was very generally the case. It was found that the cost of screening the gallery was very little more than that of screening the doors and windows. While screening the whole gallery required much more wire netting, the work itself was very simple. Making the window and door frames brought up the cost of screening them to about the cost of screening the galleries.