THE DESCENT OR ORIGIN OF MAN 85 



is eminently distinctive of man; but as those apes wMoli 

 come nearest to Mm are destitute of this organ, its disap- 

 pearance does not relate exclusively to man. The tail often 

 differs remarkably in length within the same genus; thus in 

 some species of Macacus it is longer than the whole body, 

 and is formed of twenty- four vertebras; in others it consists 

 of a scarcely visible stump, cont^iining only three or four 

 vertebrae. In some kinds of baboons there are twenty-five, 

 while in the mandrill there are ten very small stunted caudal 

 vertebrae, or, according to Cuvier,'" sometimes only five. 

 The tail, whether it be long or short, almost always tapers 

 toward the end; and this, I presume, results from the atro- 

 phy of the terminal muscles, together with their arteries and 

 nerves, through disuse, leading to the atrophy of the termi- 

 nal bones. But no explanation can at present be given of 

 the great diversity which often occurs in its length. Here, 

 however, we are more specially concerned with the complete 

 external disappearance of the tail. Prof. Broca has recently 

 shown" that the tail in all quadrupeds consists of two por- 

 tions, generally separated abruptly from each other; the 

 basal portion consists of vertebrae, more or less perfectly 

 channelled and furnished with apophyses like ordinary ver- 

 tebrae-; whereas those of the terminal portion are not chan- 

 nelled, are almost smooth, and scarcely resemble true verte- 

 brae. A tail, though not externally visible, is really present 

 in man and the anthropomorphous apes, and is constructed 

 on exactly the same pattern in both. In the terminal por- 

 tion the vertebrae, constituting the os coccyx, are quite rudi- 

 mentary, being much reduced in size and number. In the 

 basal portion the vertebrae are likewise few, are united 

 firmly together, and are arrested in development; but they 

 have been rendered much broader and flatter than the corre- 

 sponding /ertebrae in the tails of other animals; they consti- 



9» Mr. St, George Mivart, "Proc. Zoolog. Soc," 1865, pp. 562, 583. Dr. J. 

 E. Gray, "Cat. Brit. Mus. : Skeletons." Owen, "Anatomy of Vertebrates," 

 Tol. il. p. 51 :. Isidore GeofEroy, "Hist. Nat. Gen.," torn. ii. p. 244. 



'" "EevuO d' Anthropologie, " 18'72; "La Constitution des Vert^bres cau- 

 dales." 



