931. Why are the bones of the skull divided by sutures (seams), with points which fit into each other like small teeth?
Because, by that arrangement, concussions of the skull, which might be fatal to the brain, are deadened, and injuries from accident greatly modified.
"And I will lay the sinews upon you, and will bring up flesh upon you, and cover you with skin, and put breath in you, and ye shall live; and ye shall know that I am the Lord."—Ezekiel xxxvii.
932. Why are the heart, lungs, &c., placed within the chest?
Because the functions of those organs require considerable space, while their importance in the system of life, renders it essential that they should be securely protected from the probabilities of accident.
933. Why are the heart and lungs enclosed for protection in a series of ribs, and not in a close case, like the brain?
Because, by the inflation and contraction of the lungs, their capacity is constantly changing. When man takes a moderate inspiration, he inhales about thirty cubic inches of air, and the lungs increase in size one-eighteenth of their whole capacity. Consequently, were they enclosed in a frame of fixed dimensions, it must needs be, to that extent at least, larger than is necessary, when the frame is made to dilate and contract with the capacity of the lungs.