8 FISCHER ON THE PELVIS OF THE MAMMALIA; 



enter the excavation of the pelvis obliquely ; and this indeed happens more 

 frequently with the occiput turned towards the left than the right acetab- 

 ulum, because the uterus in the commencement of pregnancy inclines sen- 

 sibly more and more towards the right side than the rectum, which is rather 

 placed towards the left side, proved perfectly by the examination of the 

 bodies of female infants. Now it was necessary that the head of the fcetus, 

 after it had entered the cavern, or cavity of the true pelvis, should again 

 slightly rotate ; because, as my measurements have at least taught me, the 

 diameter of the smaller pelvis extending from the middle of the os sacrum to 

 the middle length of the symphysis of the pubis, is a little longer than the 

 transverse diameter, measured in the same place ; which is otherwise in the 

 superior aperture of the true pelvis. The dimensions of the child's head 

 beautifully correspond to these diameters, for its transverse diameter through 

 the temples is shorter than its anterior posterior one. The lateral walls also 

 of the true pelvis, and especially the spine of the ischium, if examined care- 

 fully, seem so bent that the head of the child may of necessity be moved in 

 the manner just described. The human birth then is accomplished, as all are 

 agreed on, whilst the head of the child is turned in the pelvis by a semigyra- 

 tion, resembling the whirl of a univalve shell, and so escapes. But since the 

 effort which expels the child acts in a right line, and the immovable walls of 

 the pelvis at last produce these curved lines from a rectilinear motion, it 

 readily appears how much of the propelling force must be lost against the 

 walls by this oblique action, and how, from this cause, the human birth must 

 be difficult ; but this detriment is made up for by the erect stature, the 

 rounded head and larger brain of man, and by his elevated position above the 

 order of mammals. 



All these things are quite differently arranged in animals ; it was necessary 

 that by far the greater number of them should walk on four feet, the pelvis, 

 in consequence, bv no means supports the intestines ; on the contrary, the 

 bowels descend rather from the pelvis towards the deepest part of the um- 

 bilical region, so that, in the smaller animals at least, when they are opened 

 n a supine position, the intestines are never found filling the cavity of the 

 pelvis, as in man, but are found rolled up, and occupying the middle of the 

 abdomen. Hence it happened that the os sacrum might be narrower, and 

 very narrow it is in most of them, and seems to have such a curve with the 

 coccygeal bones as the weight of the tail requires. There is not even so much 

 of a promontory as we find in the human foetus. The head of the foetus also, 

 which in animals is not spherical as in man, but straight and elongated, cor- 

 responds to the straight course through the pelvis ; and it easily escapes 

 through it, expeditiously propelled, the propelling forces meeting with no 

 resistance from its walls. In the gravid quadruped the fundus of the uterus 

 inclines downwards by its own weight ; and its orifice looking towards the 

 pelvis, rises somewhat upwards ; but in quadrupeds also, the posterior aper- 

 ture of the pelvis leads chiefly upwards, and is there covered by a very move- 

 able and narrow sacrum and coccyx, composed of several distinct and separate 

 vertebrae. That the fcetus of the lower animals escapes from the pelvis 

 chiefly by the yielding of the bones of the coccyx upwards, also become more 

 moveable at the period of parturition, is known to every country woman, who 



