FETAL LUNGS.
The lungs, previously to the act of inspiration, are dense and solid in structure, and of a deep-red color. Their specific gravity is greater than water, in which they sink to the bottom; whereas lung which has respired will float upon that fluid. The specific gravity is, however, no test of the real weight of the lung, the respired lung being actually heavier than the fetal. Thus the weight of the fetal lung, at about the middle period of uterine life, is to the weight of the body as 1 to 60. But, after respiration, the relative weight of the lung to the entire body is as 1 to 30.