A textbook of obstetrics . Fig. 270.—Measuring the diagonal conjugatediameter (Dickinson). ANOMALIES IX THE FORCES OF LABOR. 415 between the axis of the pubis and the true conjugate, [<normal thickness of the symphysis, and a normal height of thepromontory (Figs. 271 to 275). These factors, however, arenot constant, and if they vary much from the normal, the mostskilful and most experienced obstetrician may be misled woefullyin his estimation of the true conjugate. I have had undermy care a rachitic dwarf in whom there was more than 3 cen-timeters difference between the diagonal and true co
A textbook of obstetrics . Fig. 270.—Measuring the diagonal conjugatediameter (Dickinson). ANOMALIES IX THE FORCES OF LABOR. 415 between the axis of the pubis and the true conjugate, [<normal thickness of the symphysis, and a normal height of thepromontory (Figs. 271 to 275). These factors, however, arenot constant, and if they vary much from the normal, the mostskilful and most experienced obstetrician may be misled woefullyin his estimation of the true conjugate. I have had undermy care a rachitic dwarf in whom there was more than 3 cen-timeters difference between the diagonal and true conjugates,and Pershing found, among ninety pelves in the museums ofPhiladelphia, a difference varying from centimeter to It is declared that these sources of error may beeliminated by the following corrections : For every degree of. Fig. 271.—Effect of different inclinations of the pubis upon the relationship betweenthe true and the diagonal conjugate diameter (Ribemont-Dessaignes). increase in the conjugatosymphyseal angle add half the numberof millimeters to the sum to be subtracted from the diagonalconjugate, and vice versa ; also, for every centimeter increasein the height of the symphysis over the normal add centi-meter to the sum to be subtracted from the diagonal conjugate,and vice versa. While these rules are admirable for the studyof the dried specimen in a museum, they are not easily appliedto the living pregnant female. The height of the symphysiscan be measured in the living subject, but an allowance forvariations in this respect eliminates error in only a small propor-tion of cases. The variations in the angle of the symphysis, amuch more important source of error, can only be cases upon the border-line between the relative and absolute 4i6 THE PATHOLOGY OF LABOR. indications fo
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