446 



GENERATION. 



part of largely convoluted veins of conside- 

 rable size ; but these veins are differently ar- 

 ranged in the last-mentioned of these parts 

 from what they are in the two first : first in 

 this respect, that in the glans and corpus spon- 

 giosum urethra the tortuous veins are less 

 dilated and more branched than in the corpora 

 cavernosa ; so that it is more easy to trace their 

 continuity with one another ; and, second, that 

 in the corpora cavernosa the dilated veins are 

 bound together and crossed in various direc- 

 tions by ligamentous fibres and bands, an 

 arrangement which, while it tends to obscure 

 the connection of one vein with another, and 

 causes their tortuosities to appear rather like 

 cells than continuous tubes, at the same time 

 serves to prevent their distension beyond a 

 certain point during erection, and thus adds 

 to the rigidity occasioned by the accumu- 

 lation of blood in the venous convolutions or 

 sinuses. 



The mode of union of the arteries with the 

 veins in the erectile tissue of the penis is not 

 yet well known ; for, although the arteries of 

 the penis have been traced to very small rami- 

 fications, corresponding small branches of the 

 veins have not been observed, and conse- 

 quently anatomists are nearly in complete ig- 

 norance of the nature of the small vessels of 

 communication or capillaries of the erectile 

 tissue, and are left to conjecture only respect- 

 ing the means of passage for the blood from 

 the small arteries into the cells formed by the 

 convoluted veins. Professor Miiller, of Berlin,* 

 has lately made an important step in the in- 

 vestigation of this point of structure, by the 

 discovery of a remarkable set of little dilated 

 and ramified branches appended to the termi- 

 nal twigs of the arteries distributed on the 

 sides and interspaces of the venous cavities 

 in the penis of man and several animals; 

 but so far as we are aware, the exact mode 

 of passage of the blood from these helicine 

 arteries, as they have been termed from their 

 tortuosity, has not been detected, and the 

 operation of these arterial branches in modi- 

 fying the circulation, or their relation to the 

 process of erection, has not been pointed out; 

 it appears probable that so peculiar a piece of 

 mechanism must have some connection with 

 this process. (See ERECTILE Tissueand PENIS; 

 also Figs. 98 and 99, p. 146, vol. ii.) 



The principal exciting causes of erection 

 may be referred to the following heads : 



1. Mental emotions relating to sex: in ani- 

 mals, odour of the genital organs, more espe- 

 cially in the breeding season. 



2. Nervous affections. Epilepsy, convul- 

 sions. Inflammations of the brain, and simi- 

 lar affections. 



3. Warmth or other local irritation of the 

 penis and sexual organs. 



4. A full state of the testicles, their excre- 

 tory ducts or vesiculse seminales. 



* See his Archiv. fur Physiol. &c. 1835, pp. 27 

 and 220, and his paper, " Ueber die organischen 

 Nerven der erectilen mannlichen Geschlectsor- 

 gane/' in the Abhand. d. k. Akad. d. Wissensch. 

 v. Berlin fur 1835. 



5. Irritation of the parts in the vicinity of 

 the penis, as of the urinary bladder by stone, 

 riding, cantharides, savine, alcohol, &c.; of the 

 rectum by strong purgatives; and, in short, 

 every thing which irritates or determines a 

 greater than usual flow of blood to the pelvic 

 viscera or sexual organs. 



6. Ligatures, and all other causes of ob- 

 struction to the return of blood from the 

 penis. 



Erection is an involuntary act ; for we have 

 neither the power directly to produce it, nor, 

 when it occurs, to recall the state of collapse. 

 When the penis is in the state of erection, 

 however, the rigidity may be increased by the 

 voluntary exertion of the ischio-cavernosi or 

 erectores penis, and the acceleratores urinae 

 muscles ; and no doubt also by the action of 

 the muscles lately described by Dr. Houston* 

 under the name of compressores venae dorsalis 

 penis, to the contraction of which, and the 

 consequent impediment produced to the return 

 of blood from the penis, that anatomist has 

 attributed in a great measure the erection of 

 the organ. 



The turgescence of erection begins at the 

 root of the penis in the corpora cavernosa, and 

 at the glans in the corpus spongiosum. The 

 glans and spongy body of the urethra may, 

 in general, be made to collapse by pressure, 

 but the corpora cavernosa cannot unless the 

 erectile action itself ceases. The arteries of 

 the penis appear to beat with more than usual 

 force during erection. 



The phenomenon of erection is not confined 

 to the penis or such parts as are provided with 

 muscles, but occurs in all situations where 

 that arrangement of the bloodvessels consti- 

 tuting the erectile tissue is to be found. The 

 nipple of the mamma, the cock's comb and 

 wattles, and the turkey's neck are all affected 

 in a similar way ; and, although some circum- 

 stances seem to shew that erection may in 

 some instances be promoted by muscular con- 

 traction, we are inclined to adopt the opinion 

 that it is mainly due to an altered condition 

 of the bloodvessels themselves, and that it 

 may in some degree be analogous to the dila- 

 tation of the bloodvessels which occurs in 

 blushing, and some other local determinations 

 of blood.f The large size of the numerous 

 nerves which accompany the bloodvessels of 

 the penis is also in favour of this view. 



In many animals the penis is furnished with 

 a bone which adds to its rigidity. This is the 

 rase chiefly among Cheiroptera, Quadrumana, 

 Solipeda, Digitigrada, Rodentia, Phoca, and 

 Cetacea. We refer to the articles on Com- 

 parative Anatomy for a description of the many 

 varieties in the form of the penis in different 

 animals, and their uses in the act of propa- 

 gation. 



The texture of which the glans clitoridis 

 and corpora cavernosa of that body as well as 

 the nymphae are formed, is of an erectile kind 

 and strictly analogous to the corresponding 



* Dublin Hospital Reports, vol. v. 



t See the article CIRCULATION, vol. i. p. 672. 



