The mammals, to which, views zoologically, also we people belong, is warm-blooded, at least embryonic hairy vertebrates with usually four limbs. You/they have shared heart completely in two pre-chambers and two chambers one and bear living young, that nourish her/it/them from milk-glands, normally. The warm-blooded-ness is not always interconnected with a constantly high body-temperature: As well as sewers, flutter, decay and armadillos, anteaters, insectivores, semi-monkeys and Klippschliefer alter Z her/its/their body-temperature. T. considerably, as also the winter and dry-time-sleepers. Embryonic hairy means, that some wild mammal-types arise almost or quite bare is, whales, sea-cows, rhinoceroses, elephants, river-horses, stag-boars, bare-lint, some Fledertierarten u. a.). As well, the human being has hair-loose pet-races (Z). B. Pigs (bare-dogs) bred.

Not all mammals have four limbs. With whales and sea-cows, basins and rear-extremity are strongly stunted and no externally more visible. Either all mammals are not viviparous, the sewer-animals put eggs and nourish their boys slipping from it from teat-draws lots milk-glands.

Besides this at the beginning of named characteristics, the mammals, who distinguish her/it/them from the remaining vertebrates, possess even further. Her/its/their skull carries a double Condylus or joint-humps for the first neck-fuss (atlas) as mouth-cave-roof a so-called wrong, d. h. secondary palates, at the strainer-leg of beginning nose-cave-mussels (Ethmoturbinalia) and in the inner-ear always 3 hearing-ankle-little.

The lower jaw consists of one bone only each on both sides, that is tooth-bearer (dental) at the same time. In the upper jaw, only jaws and inter-jaws possess, however not also the palate, teeth. These are normally diverse, d. h. in edge, corner, and cheek-teeth apportioned. At most two tooth-consequences become after the birth or - taken generations in use.

The number of the neck-fuss amounts to only seven (exception): Sloth with 6-9 and sea-cows with Z. T. 6; Additional-ribs are missing. Breast and abdominal cavity is completely of each other separately through a diaphragm.

The brain is big, develops the bark particularly at the cerebrum. The cerebrum-halves are together interconnected through a fore bridge (Commissura) and the beam (Corpus callosum).

Only the 4. left arterial-bow remains in use as Aortenbogen. The red blood corpuscles are seedless, round (with camels oval) and bikonkav. From the kidneys, only the so-called permanent kidneys are active as Ausführorgane after the birth. Besides the milk-glands, perspiration-glands and tallow-glands are still developed own face-skin-muscles as skin-glands and at the head as well.

With the limb-claim-bones, a cartilage-layer remains between the joint-ends (Epiphysen) and the shaft (Diaphyse) as growth-zone, that, in contrast to the reptiles, also later ossifies and finishes the growth with it.