46 OF THE PELVIS. 



being graduated externally, it is easy to estimate the distance that 

 separates the two vertical pieces. In this manner we can measure 

 the sacro-pubic diameter with the most rigid exactness on the dried 

 pelvis, but in living women, Coutouly's instrument is rarely applicable, 

 except in the case of pregnancy ; it is not so, however, in a woman 

 in labor, if the summit of the head be engaged in the strait; besides, 

 when it can be made use of, its introduction must always be very 

 painful, and its results will be most generally fallacious. This pel- 

 vimeter therefore deserves the neglect into which it has sunk. 

 Many accoucheurs have endeavored to find a substitute, but as 

 those they have proposed have not fulfilled the ends intended by their 

 authors, any better than Coutouly's, they have been quite as little 

 employed as his. The thimble with which Asdrubali armed the 

 fore finger, in order to increase its length ; the sort of foot rule, 

 in the shape of a compass or pincers, with branches of unequal 

 lengths, which can be opened in the pelvis; those made with the arms 

 straight, hollow, or full and graduated, according to the plans of 

 Stein, Creve, and Aitken, aflTord us results not at all more precise 

 than the others. 



119. The internal mensuration may be well effected by the fingers 

 or hand. When the woman is not in labor, or when the head is not 

 as yet engaged, the point of the fore finger may readily be carried 

 to the promontory : the root of the finger is then raised up against 

 the arch of the pubis, and the place where it touches is marked with 

 a finger nail of the other hand. Nothing can be easier after this 

 than to ascertain the distance from pubis to sacrum. Unlike other 

 pelvimeters, the finger is a feeling instrument, the point of which 

 will not slip away from the promontory of the sacrum without the 

 operator knowing it ; thus one of the most frequent causes of error 

 is at once obviated. It is true, that as the line represented by the 

 finger falls below, and not on a level with the top of the symphysis, 

 as it ought to do, we commonly find the length greater than it ought 

 in reality to be, but by subtracting four or five lines on account 

 of this obliquity, we shall have for tlie remainder pretty exactly the 

 measurement of the space between the sacro-vertebral angle, and 

 the top of the symphysis pubis. There are two circumstances, how- 

 ever, that may easily lead us into error. The first is where the 

 upper edge of the symphysis seems to have fallen backwards ; and 

 the second, where the contrary obtains. Here indeed the antero- 

 posterior diameter, of the superior strait, might appear very great, 

 although in fact it were very small, and reciprocally. But the appli- 

 cation of the calliper externally would readily correct the mistake 

 likely to arise from such a disposition of the bones. 



