INTEOBUGTION. 3 



every person possesses at least two names, a Christian 

 name and a surname. The generic name comes first, 

 and is, of course, common to all animals of the same 

 genus. The second name is the specific one, and 

 belongs exclusively to animals of the same species. 

 The hare and rabbit, for example, are both included in 

 the genus Lepus. The Latin name of the first is Lepus 

 timidus ; that of the second, Lepus cuniculus. Horse 

 = Equus caballus ; ass = JEquus asinus. 



II. Review of the Structure and Vital Phenomena of 

 Animals. 



I select as a point of departure the human body, 

 and the bodies of domestic animals, because my readers 

 are best acquainted with these. 



The limbs consist, beginning on the outside, of skin, 

 flesh, and bone. The same parts ca.n also be distin- 

 guished in the head, neck, and trunk ; but in these 

 divisions of the body they enclose a cavity, the 

 body -cavity, which, again, contains various parts 

 (" organs "), which are not everywhere attached to the 

 body-wall. Fig. 1 represents a longitudinal section 

 through the body. The skin is represented by a line, 

 flesh and internal lining are shaded, while the bones 

 are black. These parts form together the body-wall. 

 In front the body-wall encloses a cavity, the body- 

 cavity (Kh.), which in Mammals is divided into two 

 sections (thoracic cavity, Bz.h, and abdominal cavity, 

 B.h.) by the midriff (diaphragm). In the thoracic 

 cavity are found the lungs and heart (H), also most 

 of the gullet or upper part of the gut ; the abdominal 

 cavity contains the remainder of the often much-coiled 

 gut, which in one place widens into the stomach (if), 

 also the kidneys, spleen, and parts connected with the 

 gut (e.g. the liver). The cavities are bounded behind 

 by the backbone (vertebral column), which is made up 

 of many flattened vertebrae. The uppermost vertebra 



