POSTNATAL GROWTH OF HEART, KIDNEYS, LIVER, AND SPLEEN. 269 



growth of the liver from 3 to 12 months is greater than that of the heart, and less 

 than that of the kidneys. 



The liver of the female is smaller than that of the male except at about the 

 age of 10 years, when it exceeds the latter in size. This corresponds to stature and 

 heart weight and is evidence of precocity in the female. The liver of the negro is 

 smaller than that of the white up to the age of 14 years; after that age the liver of 

 the negro female seems to exceed in weight that of the white female. However, 

 more data are necessary to confirm this. 



The weight of the liver at all ages falls naturally into two groups large and 

 small. This difference in size is especially noticeable after the age of 14 years, at 

 which time the weight may be subdivided into four groups. This is true also for 

 the other organs, but with them it is not so distinct. The extremely small livers 

 are from individuals who have died of such wasting diseases as tuberculosis, the ex- 

 tremely large ones almost exclusively from those who have died of pneumonia. This 

 organ, more than the others, seems to be affected by such diseases. The extremes 

 of weight in tuberculosis are 500 and 1,200 grams, while in pneumonia they are 1,800 

 and 2,800 grams. 



KIDNEYS. 



The two kidneys are treated as one and charted as were the heart and liver. 

 The initial increase in growth, i. e., 3 to 12 months, is greater and more rapid in 

 the kidneys than in the other organs, and their maturity seems to be reached earlier, 

 or at about the age of 15 years. Other than this the kidneys have corresponding 

 periods of rapid and slow growth, which fall at about the same time as those of the 

 other organs. 



The kidneys are smaller in the female than in the male except at about the age 

 of 4 years, when they are slightly larger. Their weight is at all times greater in the 

 negro female than in the white female, and inversely greater in the white male 

 than in the negro male. Only after the age of 14 years does the weight fall, to any 

 appreciable extent, into the two groups; and even then these groups are not so dis- 

 tinct as in other organs. 



SPLEEN. 



The growth of the spleen is similar to that of the other organs rapid during 

 the second 6 months of life, from 2 to 8 years, and from 14 to 18 years, with inter- 

 vening periods of slow growth. However, a few irregularities may be worthy 

 of note. A greater number of large spleens, for example, are observed at 2 weeks 

 after birth, at 7 months, and at about 7 and 10 years; and more small spleens 

 about the ages of 6 and 13 years. In the male the weight of the spleen remains 

 practically the same from the sixth month to 2 years. In males the weight is 

 always greater than in females, but there is little difference between the sexes at 

 the ages of 8 and 12 years. It is likewise greater in whites than in negroes, at 

 all ages and in both sexes. This seems to be a distinct racial difference. After 

 the age of 14 years, but not before, the spleen weight may be grouped at about 

 100 grams and 200 grams, thus representing two types. 



