(350 DR MATTHEWS DUNCAN ON A LOWER LIMIT TO THE 



adult foetus exceeds either of these weights, we are led to the conclusion that in 

 the easiest labours almost no resistance is encountered by the child ; that it 

 glides into the world propelled by the smallest force capable of doing so ; that, 

 with the mother in a favourable position, the weight of the child is enough to 

 bring it into the world — a result which many clinical facts at least appear to 

 confirm. 



Having thus given Poppel's and my own estimate of the force exerted in 

 natural parturition of the easiest kind, I can at present offer nothing positive from 

 which to calculate the strength of labour in the general run of cases. My belief is 

 that in ordinary labours the power exerted is not in general much above the lower 

 limit ; but other accoucheurs may see reason to entertain different opinions. 



The higher limit of the poAver exerted in natural parturition has been 

 variously estimated. There is an easy and obvious method of arriving at it. 

 Cases are frequently occurring in which labour is artificially terminated by 

 forceps, in circumstances which leave no doubt that, under delay, they would 

 have come with difficulty to a spontaneous conclusion. The power exerted by the 

 forceps in such cases can be measured. Such measurements are not to be at once 

 taken as the power of labour necessary to finish such cases ; but when all of the 

 various sources of error are considered and included, they are of much value. 

 The chief of such sources of error are the neglect of the assistance that may 

 be afforded to the operator by the natural expulsive efforts, and the including 

 of such forces exerted by the forceps as may be unnecessary for carrying on the 

 process ; for example, prematurely applied force, or force applied so as to 

 advance the birth too hastily, or force lost by being used in a wrong direction. 

 For the making of observations of this kind by the forceps special instruments 

 have been invented by Kristeller and Joulin. 



But forceps-cases do not afford the only evidence available as to the higher 

 limit. Experiments can be made on the dead subject which can be very Avell 

 relied upon, as reproducing correctly the difficulty encountered in the living, and 

 the power required to overcome it. Such experiments have been made by Joulin,* 

 and when suitably arranged, give us the power exerted in cases which may be 

 spontaneous^ terminated by the most powerful parturient efforts ; and, it may 

 be added, with great risk of the mother's life. 



Speaking of these experiments, Joulin makes the following remarks :| — 

 " Spontaneous delivery has been sometimes observed in circumstances almost 

 identical. It appears to me, therefore, possible to admit that the figure of 50 

 kilogrammes (about a hundredweight) of force represents very nearly the maxi- 



* Memoires de l'Academie Imperiale de Medecine. Tome xxvii. p. 90, &c. See also his Me- 

 moire sur l'emploi de la Force in Obstetrique. Archives generales de Medecine : numeros Fevrier et 

 Mars 1867. 



t Traite complet d'Accouchements, p. 477. 



