i9i i.] Influence of Ventilation on Milk Yield. 233 



culosis. Numerous experiments * have been carried out by 

 the Highland and Agricultural Society of Scotland since 

 1908 in order to ascertain how far the milk production and 

 the general health of cows are influenced by warmth pro- 

 duced in this way, and whether better results would not be 

 obtained by the free admission of fresh air. The result of 

 these investigations would appear to show that in the tem- 

 peratures we are accustomed to in Britain too much impor- 

 tance has been attached to heat and too little importance to 

 fresh air. Any benefits which might have been derived 

 from the higher air temperature were nullified by the con- 

 taminated condition of the atmosphere, while the greater 

 consumption of food which was expected as the result of the 

 lower temperature has not always been experienced, owing 

 to the healthier condition and better digestion of the animals 

 enjoying the fresh air, which has enabled them to make 

 better use of their food. 



The plan followed in these experiments was to erect a 

 complete temporary division across the cow-house, dividing 

 it into two parts, one of which was freely ventilated while in 

 the other the ventilation was arranged so that except in frosty 

 weather the temperature remained steady between 6o° and 

 63 0 F., and did not exceed 65 0 . In the winter of 1909-10 

 the experiment was conducted in five byres in Scotland, all 

 being in fairly open situations. The air space per cow in the 

 byres varied considerably. Among the freely ventilated byres 

 the least space was 525 cubic feet per cow, and the greatest 

 1,268 cubic feet per cow; the less freely ventilated byres 

 varied in the same way from 480 to 1,432 cubic feet per cow. 

 Taking all the byres, the average space was 843 cubic feet 

 per cow with free ventilation and 839 with restricted ventila- 

 tion, so that the conditions may be regarded as equal in this 

 respect. 



The degree of purity of the air was tested by the proportion 

 of carbon dioxide in samples taken periodically. In this way 

 the air of the byres where the ordinary system of restricted 

 ventilation was in force was found to be much more impure 

 than that of the ventilated byres. In the former, with an 

 average temperature of 57 0 F., varying from 41 0 to 69 0 , the 



* Journal, October 1909, p. 550, and December 1909, p. 755. 



