any further perceptible increase. These phenomena are diaôÙgramôÙmaôÙtiôÙcally illustrated in Fig. 18.
Many statistics indicate a decrease of brain-weight during adult life. Boas39 was inclined to attribute this apparent phenomenon to our statistical methods, and to hold that it could ãhardly be explained in any other way than by assuming an increased death-rate among men with very large brains, at an age of about twenty years.ã But Raymond Pearl has shewn that there is evidence of a steady and very gradual decline in the weight of the brain with advancing age, beginning at or before the twentieth year, and continuing throughout adult life40.
The second part of the table shews the steadily decreasing weights of the organs in question as compared with the body; the brain falling from over 12 per cent. at birth to little over 2 per cent. at five and twenty; the heart from ôñ75 to ôñ46 per cent.; and the liver from 4ôñ57 to 2ôñ75 per cent. of the whole bodily weight.
It is plain,