_Malposition of the child.--Arm or shoulder the only faulty position of a full-grown living foetus.--Causes of malposition.--Diagnosis before and during labour.--Results where no assistance is rendered.-- Spontaneous expulsion.--Malposition complicated with deformed pelvis or spasmodically contracted uterus.--Embryulcia.--The prolapsed arm not to be put back or amputated.--Presentation of the arm and head.-- Presentation of the hand and feet.--Presentation of the head and feet.--Rupture of the uterus.--Usual seat of laceration.--Causes.-- Premonitory symptoms.--Symptoms.--Treatment.--Gastrotomy.--Rupture in the early months of pregnancy._ We have already stated that the presentations of the full-grown living foetus may be brought under three classes, viz. those of the head, of the nates or lower extremities, and of the arm or shoulder: the former two have already been considered under the head of eutocia or healthy parturition, and may be distinguished from the latter, by the great peculiarity that in them the long axis of the child's body is parallel with that of the uterus, whereas, in arm or shoulder presentations this cannot be the case, its body lying across the uterus. Although malposition of the child, strictly speaking, refers to one species of presentation only, viz. to that of the arm or shoulder, yet it has been rendered a matter of great perplexity by the speculations and theoretical notions of authors. No one has propagated more serious errors upon this subject than the celebrated Baudelocque, the more so as the great authority of his name has tended to silence all doubts as to the accuracy of his views upon this subject. Almost every author since his time has contented himself with copying more or less from him, without ascertaining by personal observation how far they corresponded with the actual course of nature. By forcing a stuffed figure into a pelvis in every possible direction, he succeeded in making actually ninety-four presentations of the child, all of which he described as if they had really occurred in nature. Few have taken so simple a view of this subject as the late Dr. Denman. "The presentations of children at the time of birth," says this distinguished accoucheur, "may be of three kinds, viz. the head, the breech or inferior extremities, the shoulder or superior extremities; the back, belly, breast or sides, properly speaking, never constitute the presenting part."