1 30 THE HUMAN SPECIES 



the large from the small intestine. In the amphibians and 

 reptiles the large intestine is straight. In the birds and, still 

 more markedly, in the mammals, and in man, it describes a 

 longitudinal and transverse course, sometimes straight and 

 sometimes coiled. The rectum alone corresponds to the 

 terminal intestine of the lower vertebrates, while the remaining 

 greater part (the colon), according to the latest research in 

 comparative anatomy, is a comparatively new acquisition of 

 mammals. 1 



Among the peculiarities of the terminal intestine the caecum 

 demands special attention, as its occurrence and development 

 are extraordinarily variable, and, where it occurs, its presence, 

 and still more that of its vermiform appendix, imparts a special 

 character to the colon. In most of the fishes, batrachians and 

 reptiles, the caecum is absent, but in the reptiles traces thereof 

 may be found. In birds its absence is rare ; where present it 

 is frequently double. Of the mammals all pachyderms and 

 ruminants possess a caecum as well as almost all the rodents, 

 marsupials, sirenia, all apes, and man. In the carnivora it is 

 either very greatly reduced, or entirely non-existent, but in the 

 ruminants it is markedly developed. 



Still more rare is the occurrence of the vermiform appendix : 

 indeed, it may be said to be absent in the majority of the 

 mammals, but is found in certain classes of the rodents (wombat, 

 mouse, rat), in the anthropoids, and in man. In man this 

 rudimentary organ varies in length from 2 to 8i to 23 cm. ; 

 among the anthropoids the length is : 



In the gibbon . . . 8'5 cm. 



gorilla . . 24 



chimpanzee . . 14 



Although in the rat and mouse it is considerably smaller, 

 corresponding to their bodily proportions, all anatomists agree 

 that, as regards the whole formation of the caecum and appendix, 

 the rat and mouse most closely resemble man. 



In the colon of man and certain of the domestic mammals, 

 the longitudinal muscular tissue lies in three fasciculi (Taenias 

 Valsalvae) ; in the pig there occur also three, in the horse first 



J A. Oppel, loc. cit., part ii., p. 591. 



