PROPERTIES OF THE UTERUS DURING GESTATION.
Pajot is right in contradicting Cazeaux's statement that in pregnancy the uterus has entirely new properties, for gestation only " increases ob scure and latent properties, that certain physiological or pathological events foreign to pregnancy may make perceptible, so that there is no doubt as to their permanence." (Pajot.) These properties are five: contractility, retractility, irritability, sensi bility and elasticity.
1st. is the great property, due of course to the muscular structure, and possessed in common with all hollow organs. The uterine fibres can actively draw together, diminishing the size of the cavity, and after a certain time can assume the original dimensions. Uterine contraction is the manifestation of this contractility.
Contractility exists in every muscular fibre, but is far more developed in the fundus and body than in the cervix.
This property, rudimentary when the uterus is empty, appears in some women at the menses, in cases of dysmenorrhoea, particularly mem branous dysmenorrhoea, polypi and fibroids; but it only reaches its cul mination during pregnancy, from the great muscular development at that period. It is greatest at the moment of delivery; and it does not cease till after death, for cases are recorded where the uterus has expelled the child after death of the mother.
Although completely involuntary, uterine contraction is not necessarily painful, as is proven by the painless contraction often experienced towards the end of pregnancy (this constitutes the concealed or secret labor of Millet and older authors). Usually, uterine contractility is accompanied with pain: hence the expression "a woman in the pains of labor." Pains and uterine contractions are terms indifferently used by authors. The pains differ in degree in different women; and may be absent. I had two well-marked cases where there were no pains.
Although involuntary uterine contraction is under nervous influence, and emotion can either suspend or induce it, it may be called into play or modified by different agents. Direct applications to the cervix (tampon, douche or dilatation), friction, massage, cold or heat applied externally, provoke contractions, which also are induced by twin pregnancy, hydram nion, death of the foetus, electricity, ergot, rue and savin; while opium in sufficient doses slows or suspends uterine contractility. Chloroform,
chloral and anaesthetics act in the same fashion.
How the nervous system acts, physiology does not tell us. Both the cerebrospinal and sympathetic systems play a part, but the latter the greater. If Oser and Schlesinger have proved that there is in the medulla oblongata a centre for uterine activity exactly similar to that which cor responds to automatic movements, it is evident that the motive power of the uterus is not called into play by central irritation, but, rather, by reflex action. The experiments of Scanzoni amply prove this; he induced delivery by applying cups to the breasts. The experiments of Kilian Spiegelberg, Kehrer, Frankenhauser, Obernier and Korner are contra dictory, as also are clinical observations. But the influence of the spine over uterine contractility cannot be denied, for in women who have para plegia, uterine contractions, if less painful, are also very feeble. And, if a few such have easy delivery, yet, in the majority, labor is tedious from feeble uterine contractions.
Brown-Skluard states that uterine contraction is due to irritation by carbonic acid, with which the venous blood is loaded. (See Causes of Delivery.) Like all muscular action uterine contractility is intermittent; and it becomes weak and exhausted when it meets too much opposition. It may persist after death. It may be regular or irregular, diminished or increased.
2d. Retractility.—" This," says Pajot, " is that property of uterine tissue by virtue of which the uterus, emptied of a part of its contents, acquires a greater thickness of its walls, while the volume and capacity diminish." It differs from contractility in as much as it is permanent, and not intermittent, and is in inverse proportion to the distension the uterus has undergone. It aims to maintain direct contact between the ovum and the uterine walls, and to prevent hemorrhage by closing the gaping vessels after delivery of the placenta, and by holding the uterus in the condition it assumes after parturition.