32 OF THE PELVIS. 



feet, and vice versa: a compensation as admirable as it is singular, 

 and which occasions danger in some measure to multiply and accu- 

 mulate around an animal in proportion as his intelligence becomes 

 more perfect. 



67. In the kangaroo and other marsupial animals, the pelvis is 

 prolonged in front by means of the spines of the pubes; which form 

 two separate bones, and support the pouch, in which the second 

 gestation of these animals is effected; its narrowness in the cabiai 

 and the mole would not admit of the escape of the young; but during 

 gestation the pieces are disjoined, and separate considerably from 

 each other. In the cetacese there are only some traces of a pelvis; 

 and in birds, reptiles and fishes, where it serves only in depositing 

 the egg, we find it gradually decomposed, until it disappears. 



§. VIII. ®f tlie recent Pelvis. 



68. The soft parts which naturally cover the interior of the pelvis, 

 produce certain changes in its form and dimensions, the knowledge 

 of which is indispensable to the accoucheur. 



69. The inferior strait, for example, is shut up by a kind of par- 

 tition, which is called the floor of the pelvis; a partition which di- 

 minishes the height of the excavation, and seems to be the antagonist 

 of the diaphragm, or rather of the abdominal muscles, during the 

 efforts of inspiration, defaecation, and the emission of urine, and dur- 

 ing parturition. 



70. This floor is composed of two fleshy layers: one, superior, 

 concave above, is formed by the levator ani and ischio-coccygeal 

 muscles; the other, inferior, concave below, is composed of the 

 sphincter ani, transversus perinei, ischio-cavernosus, and constrictor 

 vaginae muscles. There also are found the lower hemorrhoidal and 

 the internal pudic vessels and nerves, with fat and cellular tissue in 

 greater or less abundance. 



71. Lastly, it is pierced, as it were, on the median line by the 

 urethra, the vagina, and the termination of the rectum. Its lower 

 face is lined by an aponeurosis which seems to rise from the great 

 sciatic ligament, and the inner lip of the pubic arch, and the strength 

 of which, although very variable, will be found greatest as it is ex- 

 amined nearest to its origin. A portion of the pelvic aponeurosis 

 covers its upper region, and I think with Camper and M. Desor- 

 meaux, that the disposition of the fibrous laminae may exert some in- 

 fluence on the promptitude or tardiness of labor, particularly in wo- 

 men who have never had children. 



72. The superior strait is more elevated in the recent than in 

 the dried skeleton, by the entire thickness of the psoas muscles, 



