112 MAKUAL OF CATTLE- FEEDIN-G. 



If, in the pipe conducting the smoke from the stove to the chimney, 

 an exact measurement ot the volume of air pa-iSiDg" were possible, and 

 if, also, the coiuposition of the air entermg the stove and of that passing 

 out could be exactly determined m an aliquot part of it, we should 

 have all the factors needed in ordei^to determme what had been added 

 to the air that entered the stove by the fire inside it 



In the respiration apparatus the place of the stove is taken by a small 

 room, constructed of boiler-iron, serving to contain the subject of the 

 experiment. This room has Windows, cemented as air-tight as possible 

 into Its sides, and a door, provided with shdes through which the oat- 

 side air has uuhindered entrance. 



The place of the chimney is taken by large air-pumps which are kept 

 in uniform motion at any required velocity by powerful clock-work, 

 which is wound up continually by a small steam-engine. In some cases 

 this arrange ment of pumps has been replaced by a rotary blower. 



The air which is pumped out of the saloon is accurately measured 

 by means of a large gas-meter, and in order to obtain an aliquot part 

 of this air, and at the same time to analyze the air as it enters the 

 saloon, small mercury pumps are provided, which withdraw uniformly a 

 certain portion of air from that leaving the saloon and also from the air 

 just before entering it. These portions of air are accurately measured 

 by smaller meters, and their content of water and carbonic acid deter- 

 mined by absorption of the water by sulphuric acid and of the carbonic 

 acid by baryta water. 



The di&erence in water and carlDonic acid between the air a^ it enters 

 and as it leaves the saloon, calculated on the whole volume of air pass- 

 ing through it, gives the quantity added in the apparatus, i. e. , expired 

 by the animal. It will be seen that the above-described apparatus is so 

 arranged that the animal or man experimented upon is under entirely 

 normal circumstances, i. e. , under the same atmospheric pressure and 

 in an equally pure atmosphere as in a stall or ordinary room. This is 

 a great advantage, because only in this way can the expeiiment be car- 

 ried on as long as is desirable, and results obtained which are reliable 

 and correspond to natural conditions. 



By the use of the respiration apparatus, in connection 

 with analyses and weighings of food, drink, dung, and 

 urine, we are able to determine all th6 materials put into 

 and removed from the body, and thus to know the exact 

 effect of any given ration. 



