Manual of physiology for students and practitioners / by H. Willoughby Lyle.

  • Lyle, H. Willoughby.
Date:
1911
Catalogue details

Licence: In copyright

Credit: Manual of physiology for students and practitioners / by H. Willoughby Lyle. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    758/776 (page 734)
    The movements of parturition are controlled by a centre situated in the lumbar cord, entirely independent of cortical control. This is shown by some observations of Goltz. This observer transected the cord of a bitch in the dorsal region. Subsequent to the transection, it exhibited the phenomena of heat (menstruation). It was impregnated, and a normal pregnancy and parturition followed. More recently still, Goltz and Ewald have demonstrated that even the presence of the nerve centre is not necessary, for in a dog with complete removal of the cord below the lower dorsal region, parturition succeeded a normal pregnancy. The sensory nerves involved in the reflex, if any, remain undiscovered. The motor nerves concerned are the third, fourth, and the fifth lumbar nerves which supply autonomic fibres via the hypogastric nerves. It is well known that emotions, e.g. anger, rage, are able to exert an effect upon the centre. The reason for parturition is not known, though many hypotheses have been advanced, such as the distension of the uterus, pressure of the foetus, the accumulation of carbon dioxide in the blood, degenerative changes in the placenta, and the presence of hormones in the maternal blood, pro- duced either by the foetus or the placenta. After parturition is completed the puerperium ensues. During this period the reproductive organs gradually return to the condition in which they were before pregnancy oc- curred. The breasts become active, so as to perform the function of lactation (vide p. 77). The changes which occur in the uterus are known as involution, and during the process of involution, which occupies six to eight weeks, the uterus gradually diminishes in size. This change appears to be due to the activity of autolytic enzymes, and not, as is usually alleged, to fatty de- generation of the uterine wall.