The anthropometric examinations given in the University of Porto Rico during the last two years have provided data from which to determine the physical development of the Porto Rican. A total of 1,412 examinations has been made, including 616 men and 796 women. These students ranged in age from fifteen to thirty years.

A comparison of the physical development of American and Porto Rican boys and girls of the same age shows that the Porto Rican surpasses the American in nearly every point, at the ages of fifteen, sixteen, and seventeen. At eighteen the physical development is about the same, but from that time there seems to be little additional growth on the part of the Porto Rican, while the American continues to develop up to and including the twenty-second year. This seems to confirm the generally accepted theory that a person matures earlier in the tropics than he does in a temperate climate. That the slighter physical development is the effect of geographic or climatic conditions, and is not entirely due to race, is proved by the fact that measurements of Chilean boys, who are of Spanish blood, more nearly approximate those of North American boys than they do those of Porto Ricans. The following tables show a comparison of the development of the Porto Rican students with the average development of American men and women. The measurements are in pounds and inches.

If it is true that the Porto Rican reaches the height of physical development at the age of eighteen, then we may consider that an average of the measurements of the men and women from and after that age will give us what is practically the representative physical development of the Porto Rican adult. These averages are found in the following table.

Table III
Representative development of Porto Rican students at the University of Porto Rico, of more than 18 years of age.

For the purpose of comparing the Porto Rican boys with boys of Spanish blood, but of another climate, Table IV, which shows the comparative development of Porto Rican and Chilean boys from 16 to 20 years of age, is given. The measurements for the Chilean boys were furnished by the Museo Nacional of Santiago, Chili.

A study of the census of 1910 showing the distribution of the population of Porto Rico by race and by age periods gives some interesting information. If the situation given there is taken to be typical of general conditions, by considering the number of children of each class under one year of age, we find that the highest birth rate is among the mulattoes; next in order come the native whites of native parentage, next the blacks, and last the native whites of foreign or mixed parentage. The actual percentage of each class under one year of age is as follows: mulattoes, 3.9 per cent; native whites of native parentage, 3.6 per cent; blacks, 2.5 per cent; native whites of foreign or mixed parentage, 2 per cent. The percentage of the population under five years of age in each class tends to confirm this statement. It is as follows: mulattoes 17.9 per cent; native whites of native parentage, 14.7 per cent; blacks, 12.2 per cent; native whites of foreign or mixed parentage, 9.5 per cent.

While the mulattoes have the highest birth rate, it is also true that, as a general thing, they are the shortest lived of any of the classes mentioned. The class which generally has greatest longevity consists of the negroes; next in order come the native whites of mixed or foreign parentage, then the native whites of native parentage, and last, the mulattoes. Thus the order, as regards length of life, is nearly the reverse of what it is as regards birth rate.

It is observed also that while native whites of foreign or mixed parentage have a comparatively great length of life and a comparatively low birth rate, their children, who fall in the class of native whites of native parentage, have shorter lives and tend to produce larger families, than did the parents. In each class the females outnumber the males, the proportion being 100 females to 99.4 males for the total population, which, however, includes the foreign-born whites, where the males outnumber the females. In the classes of native-born citizens, the difference between the numbers of the sexes is greater than the ratio for the total population would indicate, being the greatest among the mulattoes, where the ratio is 93.6 males for every 100 females. In each class it is found that the women enjoy greater length of life than do the men.

The following table shows what proportion of the total number of each class of the population falls under the age groups designated.

It will be noticed that above the age of 55 there is a larger proportion of women than men in each class. Judging the median age for each group to be the year which divides the total number of that group into two equal divisions, so far as number is concerned, we find the following median ages: blacks, 23; mulattoes, 18; native whites of native parentage, 20; native whites of foreign or mixed parentage, 22; foreign-born whites, 37. These results correspond exactly with the statements previously made regarding the longevity of each group. This would, of course, only give the median age for each class at the time the census was taken, in 1910, but as practically the same age distribution is also found in the census of 1899, it may be concluded that the results are approximately correct. This means that 50 per cent of each group does not live beyond the age indicated, and is sometimes known as the "mean length of life." Data for calculating the average length of life are not available.

A comparison of the age groups in the United States and in Porto Rico shows that the proportion in the younger ages is greater in Porto Rico than it is in the United States.

Undoubtedly the work of the Department of Sanitation and of the Institute of Tropical Medicine will do much to change the death rate within the next few years, and to prolong life. We may well expect the next census to show a much larger percentage of the population in the higher age groups.