62 ILLINOIS ACADEMY OF SCIENCE 



The first part of this table is just as it is furnished by 

 the Holstein-Friesian Association for 1913. The second 

 part is a tabulation made from the records of 1906. The 

 reason why it was necessary to make this tabulation is 

 because the association does not classify cows over five 

 years of age, but lumps them all together. 



The cow reproduces before two years of age, and is 

 full grown at three. As further evidence that milk-pro- 

 ducing power continues to develop under milk-producing 

 exercise long after full growth, take note of the average 

 amount of milk produced by the 1,497 Jersey cows of all 

 ages tested during 1916. 



JERSEY cow MILK PRODUCTION 



YEAE RECORDS. OFFICIAL TESTS. 1916. 



Pounds 

 of 

 Ages at Calving Milk 



Under two years 6242.2 



Two years to three years 6710.0 



Three years to four years 7317.1 



Four years to five years 8040.2 



Five years to six years 8255.0 



Six years to seven years 8340.2 



Seven years to eight years 8702.2 



Eight years to nine years 8667.0 



Nine years to ten years 8643.3 



Over ten years 8900.0 



The Binet system recognizes the continued develop- 

 ment of mental power in human beings during the grow- 

 ing period, but let us go beyond that into the older life. 

 It requires mental power to learn anything, and to retain 

 it in memory while learning a second thing. It requires 

 more power to remember two things while learning a 

 third ; still more to remember three things while learning 

 a fourth ; more yet to remember four things while learn- 

 ing a fifth ; and so indefinitely. As a matter of fact we 

 carry more and more in our memory as the years go by, 

 and the increasing load we carry is a measure of our in- 

 creasing mental power. Even those persons designated 

 as feeble-minded carry more and more in their memories 

 as they grow older, and that fact is conclusive evidence 



