Several reasons have been assigned why the straining pains should come on at this stage. It cannot be owing to the pressure of the head upon the parts of the pelvis, as has been supposed and especially the rectum, thus producing the sensation of a violent desire to evacuate the bowels, because, in almost every case of first labour, the head for several days before the actual commencement of labour is sufficiently deep in the pelvis to produce these effects. It evidently arises from a sympathetic connexion "between the os uteri and vagina on the one hand, and the abdominal and other muscles on the other. We see this connexion most distinctly in those difficult labours where the head is pushed down deeply in the pelvis even to the very outlet, and where the os uteri which is but little dilated is protruded before it. In such cases we never see the really powerful and continued action of the abdominal muscles excited, let the head press never so forcibly upon the rectum; but as soon as the os uteri (perhaps after much suffering) has retracted over the head, the whole auxiliary action of the abdominal muscles commences." (_Ibid._ vol. ii. p. 467.) There is the same relation between these muscles and the vagina, as there is between them and the rectum: the moment the vagina becomes distended, it begins to contract upon the distending body, and like the rectum excites them to strong and involuntary action. The tenesmus of dysentery is a sympathetic action of the same nature; the rectum is highly irritated by the acrid nature of its contents, and excites an irresistible disposition to bear down. The patient wishes for the next pain and yet she dreads it, from the suffering it creates, and the tremendous effort which it compels her to make; the pulse is quicker, and is not only so during the intervals, but undergoes a greater increase of rapidity during the pains themselves than in the first stage; the face becomes red, swollen, and bathed in perspiration; the breath is hurried; the lips are apart; the eyes are wild; every thing betokens a state of the highest excitement. When a pain comes on, she catches hold of whatever she can reach, plants her feet upon any thing which is firm, and, by thus fixing her extremities, she is enabled to bear down with greater power and effect. During the struggle the face often changes its expression surprisingly, so much so, that even her own attendants would scarcely recognise her.