68 GROWTH IN TOTAL BODY WEIGHT 



Using the rats from the colony maintained for the experiments 

 of Osborne and Mendel at the Connecticut Agricultural Station 

 in New Haven, Ferry ('13) has recorded the growth with age 

 from the 10th to the 280th day of life. 



The diet of the rats consisted of Austin's dog-biscuit, and 

 sunflower seeds with fresh vegetables (chiefly carrots or corn and 

 string beans) two or three times a week, and a small amount of 

 cooked meat twice a week. A little salt was always kept in the 

 cage. The cages were small. 



Table 66 gives the numbers of rats weighed at the several ages 

 and table 65 the mean values for each sex. The females were 

 unmated. In chart 2 graph B shows the values for the males and 

 in chart 3 graph B shows the values for the females. 



The broken line record marked B' in chart 2 gives the values 

 found in column 2, table 65, and probably gives the truer picture 

 for the normal weight change. 



Finally at The Wistar Institute King (MS '15) has conducted 

 two series of observations (1912-1913) (1913-1915) on the in- 

 crease in body weight with age in stock Albinos. There were 23 

 males and 23 females in the first series and 27 of each sex in the 

 second. The records for the two series have been combined. 

 The observations extend from 13— 185 days and the weighings 

 were made at the ages given in table 67. These rats received a 

 'scrap' diet (i.e., a diet composed of table refuse from which 

 materials known to be injurious had been removed) . 



In chart 2 the record for the males is given by graph C and in 

 chart 3 the record for the females by graph C. In chart 4 the 

 graphs for both sexes appear extended to 485 days. 



In 1913 Jackson ('13) published a series of body weights for 

 both sexes according to age, but as these animals did not grow 

 well after about 70 days of age, the table has not been copied here. 

 On comparing the graphs for the males in the several series — 

 (see chart 2) it appears that the males reared by King grew best 

 — while in the graphs for the females (chart 3) the record by 

 Ferry shows the poorest growth for the females. It appears 

 therefore that laboratory conditions including diet (assumed in 

 each case to be wholesome) may modify the growth and that 

 the two sexes are not necessarily affected to a like degree. 



