THE EMl'Li>y.ME.\T OF FOIiCE IX I>YSToKIA. 525 



external traction which determines its progression outwards ; at the 

 same time, tliis compression produces a kind of reaction in the body of 

 the fcL'tus, and gives rise to an eccentric pressure against the walls of 

 the passage, related to that which itself experiences. The question is, 

 therefore, limited to the amount of force necessary to overcome the 

 resistance that prevents the onward progress of the fcetus, without 

 injuring either the latter or the parent. In veterinary obstetrics we have 

 no lixed data to rely upon ; but the experiments of Joulin, Delore, and 

 PouUet, alluded to by Saint-Cyr, may ailord some idea of the resistance 

 oflered by the pelvic girdle to the eccentric pressure. These authorities 

 found that if a rounded body — a ball, for instance, to represent the head 

 of a fa'tus — is attempted to be pulled through the pelvis of a woman, it 

 requires a force represented by 375 to 441, and even as much as G3o 

 pounds (estimated by the dynamometer), to produce such serious 

 lesions as fracture in the bones or disunion of the symphyses. But it 

 must not be concluded, from this result, that such powerful traction can 

 be practised with impunity in woman. In the first place, the child could 

 not be extracted alive, for its existence appears to be compromised if the 

 degree of traction by the forceps exceeds from 132 to 154 pounds ; and 

 in order that the pelvis of woman could resist such pressure, certain 

 conditions are required which we never meet with in ordinary practice; 

 for instance, the pressure should be equally applied to every part of the 

 bony girdle in contact with the head of the fcjutus. But tliis does not 

 take place with the ordinary forceps, which, even in the hands of the 

 most expert accoucheur, not only acts as a traction agent, but at a 

 given moment is unfortunately transformed into a lever of the first or 

 second kind, whose power is incalculable, and which, resting on two 

 opposite points of the pelvic circumference, may burst it, without the 

 dynamometer showing anything more than a relatively feeble degree of 

 traction. 



Otherwise, it is not only the bones which have to be considered, but 

 also the soft parts, which, pressed between the fa'tal head and the hard 

 pelvic circumference, may be bruised, crushed, or lacerated to a variable 

 degree, if the compression exceeds a certain limit. This pressure, how- 

 ever, is always considerable ; for, according to Chassagny, when a 

 tractile force of fifty kilogrammes is exercised on the head of a fcetus 

 seized by the ordinary forceps, we may calculate that each square centi- 

 metre of surface of the pelvic walls sustaius a pressure of 1,H0() grannnes, 

 even in the most favourable conditions ; though it may be as much as 

 six kilogranmies or more, according to circumstances. 



These obser\ations, though doubtless valuable and significant for the 

 accoucheur of woman, are only very indirectly applicable to veterinary 

 obstetricy. Without taking into account the strength of the pelvic 

 osseous girdle, so much greater in the Mare and Cow than in won)an, 

 several other circumstances enable us to understand why this bony circle 

 may, in these animals, resist an amount of strain which would appear 

 to be altogether unreasonable, if judged according to the principles which 

 should guide the practice of the human obstetrist. But tlic veterinarian 

 is in possession of means of traction which give him a great advantage 

 in this respect — an advantage which the accoucheur has not yet been 

 able to avail himself of ; we allude to the cords the former so frequently 

 employs as traction agents, and which can never be transformed into 

 levers, like the forceps. 



In woman, as with animals, the foetus, in passing through the pelvic 



