British medical journal . in spitoof the specialization that exists in the vertebral elements01 the Chelonian neck. The best known example of amissing vertebra occurs in the sea cow or manatee. Asall students of human osteology know, this mammal liassix, instead of seven, cervical vertebrae. Ktikenthal dis-covered another curious feature in this weird mammal:the fetal manatee has a thick coating of rudimentary hair,but the skin of the adult^animal is. like that of the whale!alinoat hairless. The abundance of hair on the fetalmanatee indicates that manatees had ancestors as furryas seals. Long
British medical journal . in spitoof the specialization that exists in the vertebral elements01 the Chelonian neck. The best known example of amissing vertebra occurs in the sea cow or manatee. Asall students of human osteology know, this mammal liassix, instead of seven, cervical vertebrae. Ktikenthal dis-covered another curious feature in this weird mammal:the fetal manatee has a thick coating of rudimentary hair,but the skin of the adult^animal is. like that of the whale!alinoat hairless. The abundance of hair on the fetalmanatee indicates that manatees had ancestors as furryas seals. Long ago, .John Hunter noted that whales andsea-cows, mammals living entirely in the water, couldderive no advantage from hair, but they have an immensequantity of subcutaneous fat which is a worse conductorof heat than water. When the ancestors of the manateetook to water they lost their hair but gained fat. Embryo-logy furnishes evidence concerning kinship and thoughts may be turned in this direction when we eai. i%S;f>%V^ Fig. 2,-a calf of 2J montlis witbdewlap. Us heart in the a flat-fish. Sole, plaice, brill, dab, flounder, and halibutwhen first hatched are symmetrical and transparent; theyhave an eye on each side and swim in a vertical the fish flattens, and the facial portion of the skulltwists in such a way as to bring the eyes to the uppersurface. The hinder part of the skull that contains thebrain does not share in the twist. Sometimes a sole isfound with an eye on the white or • blind side. Holtdescribed an cxamiile in 1894. The larva of a flat-fish,so transparent when alive, is onlv rendered visible by themetallic brilliancy of the eyes, which shine through thetransparent tissues like metal beads (,J. T. Cunningham).The alteration in the position of the eve influences themode in which the little fish swims. For instance, in theflounder (Fig. 1, the left eye projects above the edge of thehead on the left side. The fish in this condition swi
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmedicine, bookyear185
