264 THE PHYSIOLOGY OF REPRODUCTION 



Although the sexual orgasm is usually accompanied by a high 

 degree of mental excitement, it is essentially a reflex action, and 

 can take place when all connection with the brain is severed by 

 transection of the spinal cord. The friction which is set up between 

 the male and female organs during coition causes a discharge of 

 motor impulses in both sexes, the uterus undergoing a series of 

 peristaltic contractions. Thus Heape ^ has described a sucking action 

 on the part of that organ in the rabbit, the os uteri dipping down 

 into the semen at the bottom of the vagina to be withdrawn again 

 in co-ordination with a rhythmical contraction by the uterine 

 muscles. At the sanie time the accessory sexual glands in the female 

 (Bartholini's glands, etc.) discharge a secretion which is added to 

 the semen. 



It is generally believed that the centre for erection lies in the 

 lumbo-sacral region of the cord.^ Numerous experiments have been 

 recorded which prove conclusively that it is not situated in the 

 upper parti of the cord or in the brain. Thus, Goltz^ showed that 

 transection of the spinal cord above the lumbar region did not 

 destroy the reflex. Brachet* also has recorded the occurrence of 

 ejaculation under a similar condition. According to Mtiller,^ only 

 the lower part of the cord need be retained in order to preserve 

 the erection reflex, since this is still present after the complete 

 destruction of the cord in the whole of the lumbar and the upper 

 part of the sacral region. Miiller was able to induce erection in a 

 dog, which had undergone this operation, by rubbing the surface of 

 the penis.^ 



It is known, however, that erection (and even ejaculation) can 

 also be induced voluntarily by stimuli conveyed from the brain (i.e. 



slightly, it will shorten, and not infrequently enter into a series of slow 

 rhythmic contractions. If cooled to 15° C. it will contract to about one- 

 quarter of its original length. (Sertoli, " Oontribution a la Physiologie 

 Gr^nferale des Muscles lisses," Arch. Ital. de Biol., vol. iii., 1883 ; Gruenhagen, 

 " Das Thermotonometer," Pfluger's Arch., voL xxxiii., 1884. See also Fletcher, 

 "Preliminary Note on the Motor and Inhibitory Nerve Endings in Smooth 

 Muscle," Proc. Phys. Soc, Jour, of Ph/s., vol. xxii., 1898.) 



^ Heape, "The Artificial Insemination of Mares," Veterinarian, 1898. 



2 See Onuf, "Notes on the Arrangement and Function of the Cell Groups 

 in the Sacral Eegion of the Spinal Cord,", Jour, of Nervo%s and Mental Diseases, 

 1899. 



^ Goltz, " Ueber das Centrum der Erectionsnerven,'' Pftnger's Arch., vol. vii., 

 1873. See also Goltz and Frensberg, " Ueber die Functionen des Lendenmarks 

 'des Hundes," P??«^er's Arch,, vol. viii:, 1874. 



* Brachet, Recherches expSri'mentales sur les ■ Fonotio^u dii Syst&me Nerveux 

 Ganglionaire, Paris, 1839. ■ , ' \ 



^ Muller, " Klinisohe und Eiperimentelle Studien iiber die Innervation der 

 Blase; etc.," Deutsche Zeitsch. f. NervenheHh., vol.' xxi., 1902. 



^ Goltz {Function d. Nervencentr. d. Froschen, Berlin, 1869) found that in the 

 frog the centre on which the copulation-clasp depends lies in the upper segment 

 of the cord.' Every part of the body of the female attracted the male, which 

 would even embrace the dead female (see also Luciani, loc. cit.). 



