. Elementary biology, animal and human. Biology. ADDITIONAL TOPICS IN HUMAN BIOLOGY 147 â By its rounded contour, the skull furnishes the best possible pro- tection for the brain. In the first place, if a blow strikes upon the head, it would be much more likely to glance off than would be the case if the sides and top were flat. Since the end of the nose and the outside ear are the most exposed portions of the head, they would, if made of bone, be in constant danger of getting broken. Cartilage, however, gives them suffi- cient permanence of form, and at the same time this elastic material, if
. Elementary biology, animal and human. Biology. ADDITIONAL TOPICS IN HUMAN BIOLOGY 147 â By its rounded contour, the skull furnishes the best possible pro- tection for the brain. In the first place, if a blow strikes upon the head, it would be much more likely to glance off than would be the case if the sides and top were flat. Since the end of the nose and the outside ear are the most exposed portions of the head, they would, if made of bone, be in constant danger of getting broken. Cartilage, however, gives them suffi- cient permanence of form, and at the same time this elastic material, if bent out of shape, at once returns to its original position as soon as the pressure is removed. The deep eye sockets seldom allow any blow to injure the eye. The drum of the ear, the three tiny bones of the middle ear, and the delicate mechanism of the itmer ear are all buried deep in the hardest part of the skull, and so these are out of fibula Fig. 45. â Knee joint. 214. Joints. â Thus far we have considered the bones of the skele- ton as though they were independent of- each other. In the Uving body, however, we know that they are firmly attached to one an- other by ligaments and muscles, and that thus a strong but mov- able framework is formed (Fig. 45). Any region in the skeleton where motion is possible between two bones is called a joint. 215. Food and the skeleton. â In the composition of bones, mineral is found to constitute about two thirds of the material, and this must be supplied by the food. Milk is a most important article of diet in early life, since in addi- tion to the other nutrients, it supplies the phosphate of lime needed for bone manufacture. In the process of refining wheat flour much of the mineral matter is lost; for this reason whole wheat flour and the coarser cereals like corn, rye, and oats are much more valuable as bone builders, and are especially needful during the period of. Please note that these images are extracted from scanned
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1912
