Having made out the presentation, we must next diagnosticate the position. Vertex presentations have two cardinal positions, viz., the right and left positions of the occiput. There may be three varieties of either position, viz., anterior, transverse or posterior. The transverse position is rare and is only a deviation from the anterior or posterior position.
The diagnosis of the position 0. L. A. is made by the aid of palpation and auscultation. Vaginal touch furnishes only unreliable information, in the majority of cases. By palpation we ascertain the character of the vertex presentation. If we endeavor to seize the head between the two hands, at the superior strait, we find that one hand penetrates farther than the hand placed on the opposite side. The flexion of the head, in volving, as it does, the depression of the occiput, tends to elevate the fore head on the opposite side, and since, in the position 0.L. A., the occiput is on the left, the hand will be arrested on the right side, i.e., on the side of the forehead. Now, since the forehead corresponds to the anterior sur face of the fathis, the back will, of necessity,be on the opposite side. The diagnosis of the cardinal position O.I.L. is thus already made. It now remains to ascertain whether it be anterior or posterior. Palpating the left side of the abdomen, one will encounter there, in front and on the left, a resisting surface which diminishes from before backward. In multi pane the sensation is sometimes less clear, for the back, as a result of the uterine obliquity, cuts the abdominal wall along a diagonal line. As Pinard remarks, a straight line drawn from the right flank to the left iliac fosse, fairly represents the direction of the resisting surface.
a. Auscultation.—The heart-sounds are heard below the horizontal line, which divides the uterus into two equal parts, in front; on the loft and below, according to Depaul, along a line uniting the left ilio-pectineal eminence and the umbilicus, but, according to Chantreuil and Tarnier, along a line passing between the umbilicus and the left anterior superior spinous process. Vaginal touch is rarely useful in recognizing the posi tion before labor.
b. During Labor.—The same signs on palpation and on auscultation. On vaginal examination the whole difficulty lies in the recognition of the sutures and of the fontanelles, and this will be easier if the examination be made after rupture of the membranes, before the formation of the caput succedaneum, i.e., soon after the rupture and between the pains. The finger is made to pass over all of the head which is accessible, until it en counters a furrow limited by bony borders. This is the sagittal suture. In order to be sure that it is the sagittal suture we must reach the anterior and posterior fontanelles. The anterior fontanelle may be recognized by its quadrangular shape, by its size, and by the fact that a suture terminates at each one of its angles. The posterior fontanelle is known by its triangular
shape, its smaller size and its three angles, at each of which a suture ends. Having recognized the sagittal suture, we must discover its direction. Nothing is easier, after the recognition of one of the fontanelles. If, for example, we find the anterior fontanelle behind and on the right, it suf fices to follow the sagittal suture away from this fontanelle, and we will find this suture crossing the pelvis in the left oblique diameter, and ending at the posterior fontanelle, which will be in front and to the left. If, however, we feel the posterior fontanelle in front and at the left, we will feel the sagittal suture following the left oblique diameter, from before backward, to the anterior fontanelle, which is placed behind and on the right. Since the posterior fontanelle corresponds to the occiput, it will necessarily show the position of the latter. Unfortunately, the fonta nelles are not always very easy of recognition. Sometimes the anterior fontanelle is very small, as a result of the ossification of the head, and may be confounded with the posterior fontanelle. We must, therefore, carefully count the sutures ending at a given fontanelle. In other cases we only find one fontanelle. If its characters are well-marked, the diag nosis is not difficult. Since the sagittal suture is the longest of all the sutures, and always ends at the other fontanelle, it will suffice to take cognizance of the direction which it follows to establish the diagnosis, provided that the situation of the fontanelle, which is felt, be known. Again, the posterior fontanelle may be very broad. In this case the three sutures will serve to distinguish it. In certain cases there are supplemen tary fontanelles. Being situated, almost always on the suture. the extent of which they seem to limit, they may momentarily lead us into error, but we can always distinguish them from the true fontanelles, by the fact that, being due to failure of ossification, they are generally the termini of only two sutures, the two prolongations of the sagittal su ture. Nevertheless, in certain cases, a sort of suture, starting from one of their borders, ends near the parietal bone, but this rudimentary suture is always short. It is necessary, moreover, to explore the whole length of the sagittal suture in these cases, and we find farther along the anterior fonta nelle or the posterior fontanelle with its typical characters. Another cause of difficulty is a large esprit succedaneum which hides the sutureaand fon tanelles. In this case, the diagnosis is very difficult, so much so that we have even seen experienced men deceived. In such cases, auscultation is of great assistance in diagnosticating the position.