Dr. Lyon Playfair on the Milk of the Cow. 283 



boiling water (212°). The solid residue was digested with 

 aether, thrown upon a weighed filter, and well washed with 

 hot aether. The mixture of sugar and casein remaining on 

 the filter being again dried at 212°, indicated by its loss in 

 weight the quantity of butter dissolved by the aether. The 

 aethereal solution itself was evaporated to dryness, and con- 

 sisted of butter with colouring matter, more or less intense, 

 according to the character of the food. The mixture of 

 casein and sugar was washed with hot water, and the casein 

 remaining on the filter, after being dried at 212°, was weighed, 

 then incinerated, its ashes determined and deducted from the 

 weight of the casein. The solution of sugar, being evapo- 

 rated by a heat of 212°, yielded a residue consisting of sugar 

 of milk and of the soluble salts of the milk. This residue, 

 after being weighed, was incinerated and its ashes deter- 

 mined. These, deducted from the weight of the residue, 

 yielded the amount of sugar, and added to the ashes of the 

 casein, indicated the total amount of inorganic ingredients in 

 the milk. The ashes of the filter were of course subtracted. 

 The cow which was made the subject of the following ex- 

 periments is of the breed of short horns. I am not aware of 

 the number of days since she was delivered of her last calf. 

 When the experiments were instituted, she was in good 

 milking condition. In order to estimate the average amount 

 of her milk, I measured it for several days previous to the 

 experiments. During this time she subsisted upon after- 

 grass ; the meadow being about half a mile distant from the 

 cow-house. 



Morning's milk. Evening's milk. 

 October 5 5 quarts 4^ quarts 



6 5 4 



... 7 41 5 ... 



8 5 4 



9 5i 4 



The weather was fine for the period of the year; but the 

 nights being rather cold, on the evening of the 7th I directed 

 that the cow should be driven to the house, and remain thei^e 

 during the night. In the morning it was put out to grass, but 

 brought back in the evening. On the evening of the 9th I 

 commenced the analyses, and followed them up in consecutive 

 days. In every case the specimen of milk analysed was 

 taken from the milk-pail, after the cow had been thoroughly 

 milked, and the milk well stirred. This precaution was 

 necessary, because the separation of the cream from the milk 

 takes place in part in the udder of the cow. Hence the milk 



