Page:Popular Science Monthly Volume 1.djvu/368

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THE POPULAR SCIENCE MONTHLY.

We think we have demonstrated that, in an animal deprived of the cerebral lobes, the integrity of the movements of the whole body is perfect; that it is due to the action of the locomotive centres of activity, which is inevitable and always the same after certain excitations; moreover, that in these conditions there are a complete solidarity and compulsion of the movements, and a necessity for the members all to concur in maintaining an equilibrium; finally, that the movements of rotation are due to a disturbance in the equilibrium between the different locomotive centres.

 
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VENTILATION, AND THE REASONS FOR IT.
By ROBERT ANGUS SMITH, Ph. D., F. R. S.

IT is often asked how much fresh air we must allow to come into a room in order to keep it wholesome. The amounts vary so much that we shall never be able to answer the question as it arises in all its changes, unless we consider our reasons for ventilating.

The first is certainly the dislike to organic-smelling substances evaporated from living beings. As some of them are very volatile, a very little rise of temperature increases their amount; and, in warm weather, we require a change of air so frequently, that we cannot make any use of the carbonic-acid test. The amount of change is infinite; we require it for every breath, and we do not consider whether a door is sufficiently open; we open all doors and windows, or leave the house entirely.

Let us take the other extreme—a very cold room—an Esquimaux ice-hut. The amount of air wanted is wonderfully small; we do not know how much the carbonic acid may rise, but it must be very high. The organic matter is frozen, and is probably condensed on the ice; it may be inhaled as a solid, and in a form not to affect the smell. For a similar reason we require less ventilation in cold weather: it is not foolish, as some will endeavor to persuade us, to take less, but it is a natural instinct. We object to the cold, and we learn that heat is a more pressing want than even pure air, whether the organic matter affects our senses or not.

The next reason for ventilating is allied to the first; we say it is to produce freshness. This means that, although all the air of the room be quite new, it has received a something from the surfaces in the room which must be cleared out. This is the reason that housewives like to keep the doors and windows open, and allow the air for a time to blow through the house. This process removes the last particles from the furniture, and is that finish which polishing cannot give. If