896 SPECIAL PHYSIOLOGY. 



the principal organs is mentioned in their description. The specific 

 gravity of the entire body, with air in the lungs, is usually stated to 

 be from 1060 to 1070. As bone is the heaviest, and fat the lightest, 

 of the tissues, the specific gravity of the entire body is influenced by 

 the relative proportions of these two tissues; hence it is greater in thin 

 bony persons, but less than the average in children and women, who 

 are generally fatter than men, and also in corpulent persons of either 

 sex. But the practical buoyancy of the body in water, is, of course, 

 chiefly determined by the size of the chest and lungs, the freedom of 

 the latter from congestion or deposits, and their condition of inflation. 

 On the least inspiratory and expiratory movement the body rises or 

 sinks in water. Necessarily, the body is more buoyant in the sea than 

 in fresh water. The eifect of clothing, or of any kind of weight, is, 

 of course, adverse to buoyancy. 



Height of the Body. 



The human body continues to grow, at least up to the age of twenty- 

 five (Quetelet), and, as it would seem, even up to the age of thirty 

 years. (Danson.) The mean height of the male in Belgium, at twenty- 

 five years of age, is 66.1 inches, or 168 centimetres.* (Quetelet.) The 

 mean height of males, at twenty-one years, in Germany, is found to 

 be 68.1 inches, or 173 centimetres. (Zeising.) Measurements of 4800 

 criminals, in England, give a mean height in the male, from twenty- 

 five to thirty years, of 66.5 inches or nearly 169 centimetres. (Danson.) 

 The extreme divergence of the German measurements, must be excep- 

 tional, and due probably to too limited a number of observations. The 

 English stature is nearer to a mean. The height of the full-grown 

 female, at thirty years of age, is 62.2 inches, or 158 centimetres. 

 (Quetelet). The mean difference between the height of the sexes, is 

 about 4 inches. 



Weight of the Body. 



The estimated average weight of the body in the male, is also rather 

 less, according to Quetelet, than according to other observers. From 

 thirty to forty years of age* it is 140 Ibs., or 63.66 kilogrammes. f 

 From twenty-five to thirty years of age, the mean weight of the male, 

 according to Danson, is 143.1 Ibs., or 65 kil. Vierordt adopts the 

 result of one observation on a powerful male, aged forty-two, whose 

 weight was about 143.5 Ibs., or 65.25 kil. The weight of the female, 

 at thirty, is 121 Ibs., or 55 kil., i. e., about 22 Ibs. less than that of 

 the male ; but the weight increases in women up to the age of fifty, 

 when it is about 123.2 Ibs., or 56 kil. 



From the preceding numbers, a mean height of 5 feet 6J inches, and 

 a weight of 144 Ibs. avoirdupois, may be assumed, for the average full- 

 grown male. In the calculations made by English writers, on the 

 working power of a man, 150 Ibs. is, however, usually taken as his 

 weight. 



* A centimetre = 3937 inch. 



f A kilogramme = 2.2 Ibs. avoirdupois. 



