270 THE PHYSIOLOGY OF REPRODUCTION 



be found . outside the spinal cord in the genito-crural nerve. The 

 contraction of the vasa was of a slow and peristaltic kind, and did 

 not cease immediately the stimulus was withdrawn.^ 



Langley and Anderson, as a result of an extensive series of 

 experiments, conclude that the internal generative organs of the 

 cat and rabbit ^re supplied by fibres running out by the anterior 

 roots of the 3rd, 4th, and 5th lumbar nerves, and sometimes also 

 the 2nd. These fibres pass through the sympathetic to the inferior 

 mesenteric ganglia, and continue their course by the hypogastric 

 nerves. Stimulation of these fibres in the cat and the rabbit 

 caused strong contraction of the whole musculature of the vasa 

 deferentia and uterus masculinus (which Langley and Anderson 

 regard as the physiological homologue of the vesiculfe seminales in 

 these animals). The vas deferens in contracting was observed to 

 become from one to three centimetres shorter, so that there could 

 be no doubt that the longitudinal muscular coat took part in the 

 process. The contraction ■ was strong enough to cause emission of 

 semen from the aperture of the penis. It would appear, therefore, 

 that ejaculation occurred- without erection. In the dog, in which 

 the lohgititdinal muscle layer is fiot well developed, the contraction 

 of the va;s-- deferens, on excitation of the upper lumbar nerves, was 

 not nearly sb pronounced. 



Langley and- Anderson found that stimulation of the sacral nerves 

 had no effect on the internal generative organs. These are innervated 

 exclusively from the lumbar nerves, as above described.^ 



In view of the facts which have been related, it would appear 

 that ejaculation is a reflex act of some complexity involving more 

 than one centre in the spinal cord. The centre for the final expulsion 

 of the semen must be the same as that for erection, since the muscular 

 mechanisms concerned are to a large extent identical in each case. 

 The centre presiding over the internal generative organs is apparently 

 in the lumbar spinal cord. As already mentioned, Brachet observed 



1 There has been some disagreement as to whether the vas deferens under- 

 goes true peristaltic movement. According to Budge (loc. cit.) this does occur 

 in the rabbit and cat. Tick confirmed Budge for these animals (" Ueber das 

 Vas deferens," Mailer's Arekiv, 1856), but found no peristalsis in the dog 

 (c/. Langley and Anderson for the dog). On the other hand, Loeb (loo. cit.) 

 could discern no peristaltic movement in the vas deferens of the rabbit, but 

 only a powerful contraction. Nagel, who has more recently investigated 

 the question, states that the vas deferens in the rabbit does not undergo a 

 true peristaltic movement, but a simple quick contraction which suffices for 

 the emptying the tube (" Contractilitat und Eeizbarkeit des Samenleiters," 

 Verhandl. d. Phys. Oesell. zu Berlin; Arch. f. Anat. u. Phys., Phys. Abth., 

 1905, Suppl. See also Nagel, Handhuch der Phys. des Menschen, vol. ii., 

 Braunschweig, 1906). 



^ Langley and Anderson, loo. oil. That stimulation of the fibres which 

 supply the vas deferens in rabbits causes expulsive movements, without giving 

 rise to erection, was shown by M. Loeb, loo. cit. 



