LOCKED-HEAD. 491 



1099. In the first place, the case where the head is simply fixed 

 at the superior strait, because the liquor amnii has been long dis- 

 charged and the womb is closely contracted upon the body of the 

 child, must not be confounded with locked-head, nor that case where 

 it stops in the excavation, betwixt two very contracted straits, and 

 after having with great difficulty cleared the superior pelvic circle, 

 nor those in which its escape is prevented by the resistance of the 

 perineum or narrowness of the inferior strait. 



1100. The head can scarcely become locked except between the 

 pubis and the sacrum, at the superior strait; further, in order that 

 it may happen at all, the conjunction of a great number of condi- 

 tions is required; 1. That it shall present in a direct manner; 

 2. In a well formed pelvis, it must be of enormous size; 3. The 

 narrowness of the pelvic cavity shall not exceed a certain degree; 

 and there shall be a space of two inches and a half between the 

 sacrum and pubis for an antero-posterior position, or three inches 

 for a transverse position; for, locked-head cannot take place except 

 where the head can get as low down as the level of its greatest 

 thickness; 4. The uterine contractions must have been energetic. 



Among these conditions there is one upon which I must dwell 

 for an instant. I find a difficulty in conceiving how the occipito- 

 frontal diameter can really get fixed in this way in the sacro-pubic 

 diameter. The ends of the lever, which it may be considered to 

 represent, are too unequal for its occipital portion to fail to come 

 down first, especially when the efforts of the woman react violently 

 upon it through the intermedium of the vertebral column; it seems 

 to me, then, much more probable that it is the occipito-bregmatic 

 diameter that becomes locked, and that the head may be retained 

 betwixt the sacrum and pubis, as well by any one of the other dia- 

 meters of the occipito-bregmatic circumference as by the bi-parietal 

 diameter alone. 



We may further admit, along with M. Desormeaux, that locked- 

 head may sometimes take place in the excavation, when the sacrum, 

 flat, or nearly flat, makes the head pass along a canal that gradually 

 diminishes in size, as it descends, until at last it cannot turn upon 

 its axis, nor advance nor recede, beyond a few lines, tovvards the 

 superior strait. 



1101. Tumefaction of the lips of the os uteri and external organs 

 of generation, and extreme degree of swelling of the hairy scalp and 

 over-lapping of the cranial bones, have been given out as signs of 

 locked-head; but most of the phenomena may take place without 

 the locked-head, and are therefore no sufficient basis for a sure 

 diagonisis. 



