290 Dr. Lyon Play fair on the Milk of the Cow. 



food than they would do in the stall, and they consequently 

 receive a greater flow of milk. The loss experienced by the 

 greater absorption of oxygen is more than compensated for 

 by the increased appetite of the animal. 



In these experiments it will be remarked, that potatoes were 

 favourable both to the flow of milk and formation of butter. 

 This quite accords with practical experience. They abound 

 in starch, and therefore furnish the substance from which 

 butter is formed. The increase of butter in the milk of the 

 fourth day is very striking ; on this day 24 lbs. of potatoes 

 formed part of the food. The butter is also in large quantity 

 in the milk of the fifth day, though not so much so as in that 

 of the fourth, though 6 lbs. of potatoes in excess were con- 

 sumed. In these 6 lbs. of potatoes only li lb. of dry un- 

 azotised matter were furnished, which could not compensate 

 for 8 lbs. of beans (containing 4 lbs. of dry unazotised matter) 

 which had formed part of the diet of the preceding day. The 

 result is, therefore, exactly as might have been anticipated. 

 When the food contained much starch, the sugar of milk in- 

 creased in quantity as well as the butter. The large amount 

 of butter in the milk of the second day is singular, and makes 

 us regret the accident which happened to the milk of the 

 morning and prevented its analysis. A remark has often 

 been made to me by practical men (how far it is true I know 

 not), that the milk of the morning is generally richer than 

 that of the evening. As far as the limited number of analyses 

 here given warrants any conclusion, there would seem to be 

 some accuracy in this observation. The cause that it should 

 be so is apparent: during the day, when exercise is taken, 

 the number of respirations is frequent, and a large amount of 

 oxygen enters the system — this is unfavourable to the for- 

 mation of butter ; but at night, during sleep, the respirations 

 are slow, and the amount of oxygen respired is trifling. Such 

 a condition must favour the separation of oxygen from starch 

 to supply the deficiency. 



All practical experience is against the theory of Dumas, 

 regarding the formation of butter in milk, and of fat in cattle. 

 In Scotland the system of stall-feeding cows is carried to a great 

 extent. The Glasgow dairymen feed their cows in warm stalls, 

 giving them malt refuse, a few pounds of beans, steamed tur- 

 neps and potatoes, and as much pot ale (residuum after distil- 

 lation, commonly called wash) as they will drink. The malt 

 refuse consists of starch, gum, and a little saccharine matter, 

 but it is not known to contain fat. This refuse is the principal 

 food, and is very favourable to the production of butter, evi- 

 dently from its great excess of unazotised matter. The beans 



