BY H, S. HALCRO WARDLAW. 



819 



The breed and individuality of a cow are thus tlie principal 

 factors determining' its total output of milk from day to day. 

 But the amount and quality of a sample of milk, obtained from a 

 cow at any particular time, are subject to great variations, and 

 these variations are dependent on the manner in which the cow is 

 milked. It is obvious that, if a cow yields a certain amount of 

 milk per diem^ the more frequently it is milked, the smaller will be 

 the quantity obtained at each milking; for it has been shown, that 

 the number of milkings j^er diem only slightly affects the total 

 yield (Lalim and Grande, 1913). The amount of milk which is 

 obtained at a milking is proportional to the period which has 

 elapsed since the last milking. 



The quality of milk is also profoundly affected by the stage of 

 milking at which the sample is collected. This fact was known to 

 Peligot (1836), who showed that the milk first drawn from the 

 udder is considerably poorer in fat than the last portions of a 

 milking. Numerous subsequent investigations have confirmed this 

 observation, and the work on the subject was reviewed and 

 extended by Ackermann in 1913, and again by Isaachsen, Lalim, 

 and Grande in 1913. The first portion.s of a milking may contain 

 less than 1% of fat, while the last portions contain more than 

 .10%. 



The quality of the milk obtained is affected in the opposite 

 direction to the quantity by the periods which elapse between suc- 

 cessive milkings. The milk obtained after a short period of rest 

 contains a higher percentage of fat than the milk obtained after a 

 longer period (Melander, 1892; Petersen, 1894). For this reason, 

 the milk obtained in the morning, when cows are milked twice a 

 day, contains a lower percentage of fat than that in the milk of the 

 afternoon. The period elapsing between the milking in the morn- 

 ing and that in the afternoon is generally greater than that 

 elapsing between the milking in the afternoon and that on the 

 following morning. 



The food which a cow eats naturally exerts a great influence 

 on the quantity and the quality of the milk which the animal pro- 



