INFLUENCE OF NERVES ON THE UTERUS. 895 



After a time the placenta, the membranes, and the decidua constituting the after-birth are 

 expelled. 



Influence of Nerves on the Uterus. 1. Stimulation of the hypogastric plexus causes con- 

 traction of the uterus. The fibres arise from the spinal cord, from the last dorsal, and upper 

 three or four lumbar nerves, run into the sympathetic, aud then reach the hypogastric plexus 

 (Frankenhauser). 2. Stimulation of the nervi erigentes, which are derived from the sacral 

 plexus, causes movement (v. Bosch and Hofmann). 3. Stimulation of the lumbar and sacral 

 parts of the cord causes powerful movements (Spiegelberg). There is a centre for the act of 

 parturition in the lumbar region of the cord ( 362, 6). The uterus, like the intestine, prob- 

 ably contains independent or parenchymatous nerve-centres (Korner), which can be excited by 

 suspension of the respiration, and by anaemia (by compressing the aorta, or rapid hemorrhage). 

 Decrease of the bodily temperature diminishes, while an increase of the temperature increases 

 the movement, which, however, ceases during high fever (Fromme). The experiments made by 

 Rein upon bitches show that, if all the nerves going to the uterus be divided, practically all the 

 functions connected with conception, pregnancy, and parturition can take place, even although 

 the uterus is separated from all its cerebro-spinal connections. Hence, we must look to the 

 presence of some automatic ganglia in the uterus itself. According to Dembo, there is a 

 centre in the anterior wall of the vagina of the rabbit. According to Jastreboff, the vagina of 

 the rabbit contracts rhythmically. Sclerotic acid greatly excites the uterine contractions (v. 

 Swiecicki), so does anaemia (Kronecker and Jastreboff). 4. The uterus contracts reflexly on 

 stimulating the central end of the sciatic nerve (v. Basch and Hofmann), the central end of the 

 branchial plexus (Schlesinger), and the nipple (Scanzoni). 5. The uterus is supplied by vaso- 

 motor nerves (hypogastric plexus), which come from the splanchnic ; and also by vaso-dilator 

 fibres, the latter through the nervi erigentes. The vaso-motor nerves are affected reflexly by 

 stimulation of the sciatic nerve (v. Basch and Hofmann). 



[In the rabbit the vagina and uterine cornua exhibit regular movements of a "peristaltic" 

 nature. These exist apart from any extraneous stimulus, and are probably a vital property of 

 the tissue. They can be demonstrated in animals a few weeks old, and "have been recorded 

 continuously for many hours.* Frequently they are more vigorous six hours after than at the 

 beginning, showing that they are not due to the irritation of the operation necessary to demon- 

 strate them. 



Their rate and extent vary. In young animals they are frequent (1 to 4 per minute), but 

 irregular in character. In nulliparous adults they are less frequent and somewhat more 

 regular. During pregnancy they increase greatly in extent, and their rate becomes 1 in 120 to 

 130 seconds. These characters are retained after pregnancy for many months at least. They 

 are diminished or abolished by chloroform narcosis, are scarcely affected by ether. Water at 

 100 to 120 F. produces a persistent contraction accompanied by blanching of the tissue. 

 Similar effects are produced by dilute acetic acid (Milne Murray).'] 



Lochia. After birth the whole mucous membrane (decidua) is shed ; its inner 

 surface, therefore, represents a large wounded surface, on which a new mucous 

 membrane is developed. The discharge given off after birth constitutes the lochia. 



Involution of the Uterus. After birth the thick muscular mass decreases in 

 size, some of its fibres undergoing fatty degeneration. Within the lumen of the 

 blood-vessels of the uterus itself, there begins in the interna of these vessels a pro- 

 liferation of the connective-tissue elements, whereby within a few months the blood- 

 vessels so affected become completely occluded. The smooth muscular fibres of 

 the middle coat of the arteries undergo fatty degeneration. The relatively large 

 vascular spaces in the region of the placenta are filled by blood-clots, which are 

 ultimately traversed by outgrowths of the connective-tissue of the vascular walls. 



Milk-Fever. After birth, there is a peculiar action on the vaso-motor system, 

 constituting milk-fever, while at the 2nd to 3rd day there is a more copious supply 

 of blood to the mammary gland for the secretion of milk ( 231). [After birth 

 the pulse becomes slow and remains so in a normal puerperium. The so-called 

 milk-fever is not found in cases where strict cleanliness is observed during the 

 labour and puerperium.] For the cause of the first respiration in the child, see 

 p. 666. 



454. COMPARATIVE HISTORICAL. A sketch of the development of man must neces- 

 sarily have some reference to the general scheme of development in the Animal Kingdom. 

 The question as to how the numerous forms of animal life at present existing on the globe have 

 arisen has been answered in several ways. It has been asserted that each species has retained 

 its characters unchanged from the beginning, so that we speak of the " constancy of species. " 

 This view, developed by Linnaeus, Cuvier, Agassiz, and others, is opposed by that supported 



