As we have passed the upper blade behind the right acetabulum or foramen ovale, so now we must introduce the other in the opposite direction, viz. before the left sacro-iliac synchondrosis: and, as the blades being exactly opposite to each other is essential to the easy locking of the instrument, it will be necessary to guide the course of the second blade, not so much by the form of the pelvis, as by the direction of the first blade. It must, therefore, pass up, so that when introduced to its full extent, the inner surface of its handle shall correspond precisely to that of the first blade. The easy or difficult locking of the blades is a proof of their having been correctly or incorrectly introduced. If, therefore, on bringing the locks together we find that they do not correspond, that the inner surfaces of the handles are not parallel, but form an angle with each other, we must endeavour to rectify this, by withdrawing, to a short extent, that blade which deviates most from the proper direction, and pass it up again more correctly. All attempts to twist the handles so as to correspond with each other, are bad and cannot fail to put the patient to much suffering. When we are about to lock the blades, we cannot be too careful in preventing the soft parts from being pinched between them, for it causes most intolerable pain, and frequently makes the patient give such an involuntary start, as to run the risk of altering the position of the instrument. The whole process of introducing and fixing the forceps should be conducted in as gentle and gradual a manner as possible: no attempt should be made to proceed with the operation during a pain; and in no case is force either necessary or justifiable.