MALE ACCESSORY REPRODUCTIVE ORGANS 251 



THE MECHANISMS OF ERECTION, EJACULATION, AND 

 RETRACTION. 



The erection of the penis is brought about mainly by the 

 dilatation of its blood-vessels. First of all the bulbous 

 (proximal) part of the organ increases in size, and then the 

 swelling extends throughout the cavernous bodies, and eventually 

 to the glans. If the penis is cut across when in a state of re- 

 laxation only a small quantity of venous blood exudes from the 

 wound ; but if the same operation is performed during erection, 

 the blood flow is enormously increased, while simultaneously 

 becoming bright and arterial in colour. 1 Fran9ois-Franck, 2 

 observed a corresponding rise in the arterial and venous tension. 

 He found also that the organ in the process of erection became 

 very considerably swollen in size before the increase in the 

 blood pressure had extended to the veins. Loven 3 showed 

 that the veins in the penis are traversed by five times as much 

 blood during erection as they are in a state of repose. The 

 same investigator found that, whereas the ordinary arterial 

 pressure in the penis is about half that of the carotid, during 

 erection it rose to three-fifths that of the carotid. The increase 

 in the amount of blood in the organ is accompanied by a rise of 

 temperature. 4 



There can be no doubt that the erection of the penis is 

 brought about partly through the contraction of the ischio- 

 cavernosus (or erector penis) and bulbo-cavernosus muscles, 

 certain of the fibres of which pass over the efferent vessels, and so 

 arrest the outward flow of blood. 5 The result of this contraction 



1 Eckhard, " Untersuchungen iiber d. Erektion d. Penis beim Hunde," 

 Beitr. zur Anat. und Phys., vol. iii., Giessen, 1863. 



2 Fra^ois-Franck, " Rechercb.es sur 1'Innervation Vaso-motrice du Penis," 

 Arch, de Phys., 1895. 



3 Loven, Berichte iiber die Verhandlungen der Kdnigl. Sachs. Qesell. zu 

 Leipzig, vol. viii., 1866. Nikolsky, " Ein Beitrag zur Physiologie des Nervi 

 erigentes," Arch. f. Anat. u. Phys., Phys. Abth., 1879. 



* Retterer, Article on " Erection," in Richet's Dictionnaire de Physiologie, 

 vol. v., 1902. 



5 De Graaf (Regner), De Virorum Organia Generationi Inservientibus, 

 Geneva, 1785. Giinther, Untersuchungen und Erfahrungen aus dem Gebiete 

 der Anatomie, vol. i., Hanover, 1837. Kobelt, De I'Appareil du Sens Genital 

 des Deux Sexes, Strasbourg, 1851. For further references, see Retterer, toe. cit. 



