ON THE EFFECT OF STIMULATING THE NERVI ERIGENTES 

 IN CASTRATED ANIMALS. By Sutherland Simpson and 

 Francis H. A. Marshall. (From the Physiological Department, 

 University of Edinburgh.) 



(Keceived for publication llth Juhj iy08.) 



Eckhard^ was the first to show experimentally in the dog that the penis 

 could be caused to erect by the stimulation of certain nerves arising from 

 the sacral part of the spinal cord. These nerves he afterwards designated 

 the nervi erigentes. In the dog they are given off from the first and 

 second sacral nerves and sometimes also from the third, but their origin 

 from the cord varies slightly in difTerent species of mammals. Gaskell,- 

 and subsequently Morat,^ found that the nervi erigentes leave the cord 

 by the anterior roots only, and these observations have been confirmed 

 by other investigators. 



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 whose fibres pass over the efferent vessels of that organ, and so 

 arrest the outward flow of blood. The result of this contraction is that 

 whereas the blood can freely enter the dilated vascular spaces of the penis, 

 its exit is retarded. This leads to a further distension of the vessels, whose 

 venous outlets become still more compressed. It is clear, however, that 

 whereas the constriction of the outlets assists in causing erection, it is 

 incapable by itself of effecting this result, since erection cannot be induced 

 by ligaturing the efferent veins.* The usual view is that the nervi erigentes 

 exercise an inhibitory influence upon the tonicity of the walls of the vessels, 

 and so cause them to distend, and that erection is due chiefly to the direct 

 vaso-dilator action of these nerves. According to Langley and Anderson's-^ 

 description, stimulation of the nervi erigentes causes inhibition not only of 

 the unstriated muscles, but also of the retractor penis, when that muscle is 

 present. 



' Eckhard, "Untersucliungen iiber d. Erektion d. Penis beim Hunde," Beitriige zur 

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



2 Gaskell, "On the Structure, Distribution, and Function of the Nerves which innervate 

 the Visceral and Vascular Systems," Journ. of Physiol., vol. vii., 1886. 



3 Morat, " Les Nerfs Vaso-dilatjiteurs et le Loi de Majendie," Arch, de Physiol., 1890. 

 * See Retterer, article "Erection" in Richet's Dictionnaire de Physiologic, vol. v., 



1902. This article cont;iins numerous references. 



^ Langley and Anderson, "The Innervation of the Pelvis and Adjoining Viscera," 

 Journ. of Physiol , vol. xix., 1895. 



