considerable increase of our information ; and although this universal application of measurement is not required, still it shows you the contrast with the condition that I have men- tioned of a hospital that had not callipers at all. This great improvement has been introduced from Germany, and it is, in the main, an importation from Kiel. In order that you may understand it, I use the old division of mechanically difficult cases into three. You have firstly the slighter cases — and therefore the more frequent, and in that respect the more important cases — where the pelvis is spoken of as a pelvis whose conjugata vera varies between four inches and a little above three. These are the slighter cases. Now, in these cases the improvement that has been made is an improvement in our judgment of the conditions of the labour — an improved diagnosis, so that cases which are still exten- sively spoken of as cases of inertia (which is, no doubt, gene- rally an erroneous explanation, far too widely applied), or simply spoken of as " forceps cases," are now more exactly and correctly defined. They are recognised chiefly by de- viations from the ordinary progress of labour, or from the ordinary mechanism ; and these deviations from the ordi- nary mechanism are in a very great measure distinctive ; especially of cases of mere smallness of the pelvis, the pelvis being otherwise well formed ; and of cases in which the deviation of mechanism is produced by antero-posterior con- traction of the brim without the pelvis being otherwise small. This is not the place to speak further of this kind of diagnosis made during labour. I merely point it out to you because I wish you to see intelligently the interest attaching to preliminary investigations generally and in the cases that I am to bring before you at a further part of the lecture.
If we come now to graver cases — the second kind of mechanically difficult labours, where the pelvis varies from above three down to, in exceptional cases, nearly two and a
