PARTURITION, 503 



head of the puppies is usually large and round, with the forehead high, 

 and the presentation offers grave, and frequently insurmountable dii^cul- 

 ties. This is more especially the ease if the puppies are few in number, 

 when they are usually larger. 



XVII. Mechanism of Parturition in the Anterior Vertebro-Pubic Position. 



In this position the same diameters of the fo:'tus correspond to those of 

 the maternal pelvis; though in practice it is found that this position is 

 less favorable, and that delivery is always more difficult and longer than 

 in the first anterior position. This appears to be due to the fact that in 

 the latter the dorsal spines, or withers, the most prominent part of the 

 fcetus, glide along the vertebral colunm of the mother in the kind of 

 channel formed by the psoas muscles, and is naturally directed towards 

 the pelvis; Avhile in the vertebro-pubic position it comes against the brim 

 of the pubis, where greater, more frequent and more continued con- 

 tractions are needed to raise it to this kind of step leading to the inlet. 

 And when it has cleared this obstacle, the foetus still passes with difficulty 

 through the canal, as the curve of this passage is exactly the reverse of 

 that offered by the body of the foetus ; all the articulations of the vertebra?, 

 but particularly that of the atlas with the occiput, and those of all the 

 limbs, being flexed downwards, or in a contrary direction to the curve of 

 the sacrum. Conse(|uently, in order to accommr^date themselves to this 

 curvature, all these articulations must be forcibly extended — an unfavor- 

 able condition — while the pressure and friction must be considerable. And 

 not only is progress through the pelvic canal slower and more difficult, but 

 the maternal organs are also exposed to injury, and sometimes receive 

 serious damage : the feet of the fcetus having a natural tendency to be 

 carried upwards, may squeeze the vagina against the sacrum, or press 

 against the perineum, etc., when Ave may have lacerations of the vagina, 

 vulva, perineum, or other part. 



XVIII. Mechanism of Parturition in the Anterior Vertebro-IHal Positions. 



These lateral positions — two in number and symmetrical — are rarely pri- 

 mary, but are sometimes found as secondary positions, due to the reduction 

 of some malpresentations. Spontaneous birth is impossible in these po- 

 sitions, because the chest of the fcetus presents its greatest diameter to the 

 smallest diameter of the pelvis of the mother. This, however, is an exag- 

 geration, as Saint-Cyr points out that the bis-iliac diameter is sometimes 

 equal, or even superior, to the sacro-pubic diameter ; so that it is not always 

 absolutely impossible for delivery to occur spontaneously in these positions ; 

 though it is very true that it is always more difficult, and sometimes im- 

 possible, if the position is not altered. Independently of the disproportion 

 between the diameters of the pelvis and the corresponding diameters of the 



