76 OBSTETRICS. 



appears to be inexplicable. Madame Lachapelle explains their oc- 

 currence as follows : — During a great part of gestation, and whilst 

 the foetus is still movable in the cavity of the uterus, its long 

 diameter can be readily brought into coincidence with the transverse 

 diameter of that organ ; its position therefore is by no means fixed, 

 and it can, by virtue of its active movements, present any part of its 

 surface at the uterine orifice, but especially the cephalic or pelvic 

 extremities. The latter part may occupy the superior strait at any 

 period of gestation, in consequence of the movements of the foetus, 

 and may remain in that situation for an indefinite period. It hap- 

 pens then, if the foetus in this time should have developed itself to 

 any extent, it cannot turn, and it will be apt to retain the attitude it 

 may then acquire till the end of pregnancy, as its length does not 

 readily admit of its passing the transverse diameter of the uterus.* 

 Violent movements on the part of the female, it is thought, may also 

 be a cause of pelvic presentations, but as before stated, they are in 

 the great majority of cases, inexplicable. Some women, from original 

 conformation or other causes, appear particularly obnoxious to this 

 mischance, bringing all their children into the world by breech labours. 



Prognosis. — Breech labours are generally more tedious than ce- 

 phalic, inasmuch as the pelvic extremity is not so good a dilator as 

 the cephalic; it never presents the same evenness, the same resist- 

 ance, or the same rounded form as the head to the openings of the 

 pelvis ; it consequently acts to much less advantage on the cervix to 

 finish its dilatation. In vertex presentations the most voluminous 

 part, that which is best calculated to bear all kinds of pressure, es- 

 capes first. In pelvic presentations, on the contrary, the point of 

 the cone advances first, so that the foetus progresses more slowly in 

 proportion as the labour advances. 



Posilio7is. — The same difficulty occurs in enumerating the various 

 positions of the breech that we have seen obtain in the other presen- 

 tations, every author recording those which seemed to him best es- 

 tablished. Thus some make as many as eight ; among these is M. 

 Flamant, who makes one for each extremity of the different diameters 

 of the superior strait, viz.: two for the antero-posterior, two for 

 the transverse, and two for each of the oblique, making eight in all. 

 Others make six, corresponding to the different positions of the 

 vertex, the sacrum taking the place of the vertex. We find again 

 some reducing them to four, viz.: 1st, sacrum to the left acetabu- 

 lum, 2d, to the right acetabulum, 3d, to the pubes, 4th, sacrum of 

 the child to the promontory of sacrum of the mother. Thus the 

 direct positions, either anterior or posterior, are possible, as well as 

 the diagonal ones, and the breech may present in as many ways as 

 the head. 



• Chaiily, Traits Pratique de I'Art dcs Accouchemens, p. 604. 



