QUANTITY 141 



of the best of the breed, and, with this assumption, it 

 was evident that there was a high factor in the Jersey 

 producing intermediates with a low factor in the Red 

 Danish : the small fluctuations being attributed to the 

 action of factors producing a much smaller rise or fall. 

 It may be that there are two widely varying factors 

 producing intermediates, but the evidence in support 

 of this is less strong than that in support of factors 

 producing the smaller differences which are clearly to 

 be found in the Red Danish breed. Indeed it seems 

 much more likely that Count Ahlefeldt's two Jersey 

 sires carried several factors for high quality but did 

 not carry them pure. 



Some work has been done in connexion with milk 

 yield in cows, but, as yet, it is little more than pre- 

 liminary. Because of the economic importance of the 

 subject, however, this preliminary work may be dis- 

 cussed, not without profit. 



It was expected that milk should be inherited accord- 

 ing to one or other of the Mendelian schemes, and 

 evidence was sought in many directions. The earliest 

 evidence of importance came from Denmark, and it 

 indicated that there are three grades of cows giving, 

 in round numbers, 500, 750, and 1000 gallons of milk 

 during a normal lactation period. It also indicated 

 that the middle grade is a Mendelian intermediate 

 between the two extremes. At the same time con- 

 siderable deviations from these yields were revealed, 

 and it became necessary, first of all, to look into the 

 causes of these, the chief of which were found to be 

 (a) age, (6) date of calving, (c) lengths of the previous 

 and the present lactations, (d) recovery of " condition " 

 before calving, and {e) food, health, and general comfort. 



