It has been urged that the closure of the present louvres and other apertures in the side walls will restrict the necessary ventilation; I am, however, of a contrary opinion, believing that it can be demonstrated by the employment of an anemometer; _that in proportion to the exclusion of disturbing currents of air from lateral sources, will be an increase in the velocity by which the fresh incoming supply will travel through the narrow passage from front to back of the premises, and that a readier displacement of vitiated air will result_. If this should prove insufficient, a constant upward direction of ventilation can be accomplished by well-known mechanical contrivances in the roof of each house. Without reiterating the reasons which have led me to insist upon this isolation of each Slaughter-house, I will only advert to the very evident facility given for one Slaughter-house to infect its neighbour should these side openings be allowed to continue, an objection which would apply with fatal force should cattle suffering from contagious disease be imported by carelessness or design into any one of them. It being a well-ascertained fact that myriads of germs or disease-spreading organisms may be given off in the cutaneous exhalations, the excreta, and, possibly, the very breath of infected animals, it is no exaggeration to affirm that one such beast might decimate its neighbourhood, affecting alike the living cattle in the Pounds and Lairs waiting for slaughter, and the dead meat hanging up to cool in the Slaughter-house before it was carried away by the retail butchers. In the latter case, the well-known power of warm fat in rapidly absorbing all kinds of odours, good and bad, would render every precaution to prevent the contamination of the meat already killed inoperative. It is no argument against these measures to urge that their necessity has not yet been recognised by the unlearned, or to assert that no practical difficulty has arisen in the direction just mentioned, for it must be remembered that the great aim of all modern Sanitary legislation is to discover disease in its germinal condition, and apply such _preventive_ agents as will combat the extension of the mischief when once discovered.