236 NORMAL PARTURITION. 



somewhat compensated for by the greater mobility of the sacrum. And, 

 as we have seen, such is really the case, the duration of parturition being 

 shorter in the Mare than in the Cow.* 



With regard to the other animals, the same, remarks will apply. We 

 may just note that with the common-bred Bitch, which has a more or less 

 elongated muzzle, when fecundated by a Dog of the same conformation 

 and size, and which in due course brings forth from five to eight young, 

 there is usually no difficulty in delivery. The conical form of the muzzle 

 of the puppies, and the softness of their tissues, permits their entering 

 the inlet in this presentation, and passing easily through it under the in- 

 fluence of the uterine and abdominal contractions. But when the Bitch 

 is of small size, and is fecun^dated by a young, vigorous, and larger Dog, 

 and especially if the muzzle of either or both parents is short, then the 

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

 and the presentation offers grave, and frequently insurmountable difficul- 

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

 when they are usually .larger. This will be alluded to again when we 

 come to treat of difficult parturition. 



2. Mecha?iism of Parturition in the Anterior Vertebro-pubic Position. — 

 In this position, the same diameters of the foetus 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 

 foetus, glide along the vertebral column of the mother in the kind of 

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

 the pelvis ; while 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 ver- 

 tebrae, 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. Consequently, in order to accommodate themselves to 

 this curvature, all diese articulations must be forcibly extended — an un- 

 favorable condition ; while the pressure and friction must be consider- 

 able. And not only is progress through the pelvic canal slower and more 

 difficult, but the* maternal organs are also exposed to injury, and some- 

 times receive serious damage : the feet of the foetus having a natural 

 tendency to be carried upwards, may squeeze the vagina against the 

 sacrum, or press against the perineum, etc., when we may have lacera- 

 tions of the vagina, vulva, perineum, or other part. 



3. Mechanis7n of Parturition i?i the Anterior Vertebro-ilial Positions. — 

 These lateral positions — two in number and symmetrical — are, according 

 to Saint-Cyr, rarely primary, but, as Rainard remarks, are sometimes 

 found as secondary positions, due to the reduction of some mal-presenta- 

 tions. The latter authority asserts that spontaneous birth is impossible 

 in these positions, because the chest of the foetus presents its greatest 

 diameter to the smallest diameter of the pelvis of the mother. This, 

 however, is an exaggeration, as Saint-Cyr points out that the bis-iliac 



* The fact that parturition is more quickly performed in the Mare than any other quadruped was well 

 known to Aristotle : Equa, omnium quadrtipedem,facillime, parit. 



