356 THE POPULAR SCIENCE MONTHLY. 



We think we have demonstrated that, in an animal deprived of th 

 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 activ- 

 ity, 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 t<\ 

 concur in maintaining an equilibrium ; finally, that the movements of 

 rotation are due to a disturbance in the equilibrium between the dif- 

 ferent locomotive centres. 



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VENTILATION, AND THE REASONS FOR IT. 



By EOBEET ANGUS SMITH, Ph. D., F. E. S. 



XT 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 in- 

 finite ; 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 



