THE NUMERICAL DISTRIBUTION OF THE ISLETS OF LANGERHANS AT DIFFERENT AGES OF THE RAT

Abstract

ABSTRACT The mathematical relationships between the observed size distribution of the section surfaces and the actual distributions of different sized spherical and ellipsoidal bodies, postulated by Wicksell (1925, 1926) have been used to determine the numerical distributions of the islets of Langerhans in rats of different ages. Only those islets whose surface areas in the section were equal to or exceeded that of a standard circle 46.9 μ in diameter were included in the measurements. New-born rats and rats 5, 21, 100 and 480 days old were studied. The numerical distribution curves at all ages appeared asymmetrical with the smallest islets predominating. With an increased number of islets the largest size classes in general showed the greatest proportional increase both when the comparison was made in the same and between different age groups. A very high proportion of the islets studied could be arranged in the same regular pattern. In all the animals the relation between the logarithms of the islet numbers and their diameters was linear in those of the size classes studied, which contributed significantly to the total number of islets. Since the lines for any age group and the next were also approximately parallel the relative increase in the number of islets in any size class (except the very largest with only few islets) was thus nearly constant, i. e. independent of the particular size class. In comparing rats within the same or between two succeeding age groups the nearly parallel lines allow both the islet number in each of the size classes mentioned above and the total number of islets to be characterized by a parameter Lm which is the value of the line at its intercept on the Y axis.