EXCRETION. 



147 



villi of the placenta, observes : our vessels are 

 simple ; they bend themselves at the end, but 

 do not return to their trunk as a loop, being 

 simply blood-containing processes of the ar- 

 teries which project freely into the cellular 

 cavities of the veins of the corpora cavernosa. 

 These vessels are most numerous in the pos- 

 terior part of the corpora cavernosa ; they 

 occur but seldom in the middle and anterior 

 parts : they are also present in the corpus 

 spongiosum urethra, especially in the bulb; 

 here also they become less frequent anteriorly, 

 and as yet they have not been perceived in the 

 glans. They are much more difficult of detection 

 in the corpus spongiosum urethrae than in the 

 corpora cavernosa, where they are very easily 

 exhibited, especially in the human penis. In 

 no other animal have they been found so dis- 

 tinct, or so uniform in their existence as in 

 man. The greater development of these arteries, 

 adds Professor Miiller, in the posterior parts of 

 the organ corresponds with the fact of erection 

 being always earlier evident there, as if the 

 blood distributed itself from thence into the 

 venous cells. 



During erection blood is accumulated in 

 large quantity in the erectile tissue, but the 

 cause and mechanism of this accumulation are 

 but imperfectly known. Hebenstreit ascribes 

 it to a living power, named turgor vitalis, 

 which exists in different degrees in almost all 

 the textures of the animal body, but most dis- 

 tinctly in the erectile tissue. It still remains, 

 however, to be proved how far erection de- 

 pends on mechanical pressure affecting the 

 veins which convey blood from this structure, 

 and consequent retardation of the venous circu- 

 lation ; and how far it may depend upon an 

 increased flow of blood to its arteries accompa- 

 nied, or perhaps more correctly, occasioned by 

 an increase of sensibility,* or whether it may not 

 depend upon the influence of both these 

 causes combined. 



Erectile tissue appears sometimes to be de- 

 veloped as a morbid production, which has 

 been described under the names of varicose 

 tumour, aneurism by anastomosis, naevus ma- 

 teraus, telangiectasis, &c. Its anatomical cha- 

 racters are of the same kind as those of the 



[* Ii must be obvious that the discovery of the 

 artericB helicinee by Professor Miiller favours this 

 theory of erection, as proving the existence of ves- 

 sels distinct from the ordinary ones, which receive 

 and transmit the increased supply of blood to the 

 venous cells. What, in other organs, is effected 

 by a diminished tonicity in the arteries, and a con- 

 sequent enlargement of them, ultimately giving 

 rise to the tortuosity so striking in some cases, is 

 here effected by means of a very peculiar set of 

 arterial processes superadded to the ordinary nutri- 

 tious arteries of the organ. In the pregnant uterus 

 the increased supply of blood is provided for by the 

 enlargement and consequent tortuosity of its ordi- 

 nary arteries ; there are no sinuous veins here to 

 receive the new supply of blood, and consequently 

 erection is not present ; but in the case of the 

 penis this phenomenon occurs in consequence of 

 the existence of the sinuous veins which constitute 

 so large a proportion of the corpora cavernosa. It 

 will be interesting to inquire whether any similar 

 or analogous arrangement of arterial processes 

 exists in other erectile organs. ED.] 



normal erectile tissue ; it varies In size, being 

 more or less circumscribed, sometimes sur- 

 rounded by a thin fibrous envelope; presenting 

 internally an appearance of cells or spongy 

 cavities, but consisting, in reality, of an in- 

 extricable congeries of arteries and veins which 

 communicate by innumerable anastomoses 

 like capillary vessels, but much larger, espe- 

 cially the veins. It is difficult to inject it from 

 the arteries, more easy from the neighbouring 

 veins, which are sometimes much enlarged. 

 This alteration most commonly exists in the 

 substance of the skin, where it sometimes re- 

 sembles the comb and other analogous parts 

 of the gallinaceae. The skin of the face, espe- 

 cially that of the lips, is frequently its seat. 

 It has been observed in the subcutaneous cel- 

 lular tissue in masses of various dimensions, 

 sometimes so large as to occupy an entire limb. 

 It rarely affects the internal organs ; sometimes 

 it extends beneath the mucous membrane of 

 the mouth, mostly in the vicinity of the red 

 borders of the lips. This production is occa- 

 sionally affected by a vibratory motion amount- 

 ing sometimes to a pulsation resembling that 

 of an aneurismal tumour, which is increased by 

 all the causes which excite the activity of the 

 general circulation ; it cannot be properly said 

 that this structure has the property of under- 

 going erection. It is often congenital, some- 

 times it appears to have been produced by 

 accidental causes; it sometimes remains un- 

 altered ; but it more usually continues to in- 

 crease in size until some of its cavities burst, 

 when haemorrhage of a troublesome description 

 ensues. 



Beclard considers the hasmorrhoidal tumours 

 which occur round the anus as constituting a 

 variety of anormal erectile tissue. 



BIBLIOGRAPHY. Vesalius de corp. humani 

 fabrica, lib. v. cap. xiv. Venet. 1564. De 

 Graaf Regner, De virorum organis, &c. p. 99 et 

 seq. Lugd. Bat. 1668. Malpighi Marcelli opera 

 omnia, torn. ii. p. 221. London, 1686. Ruysch 

 Frid., Observatio, C. Amstel. 1691. Holier, Ele- 

 menta, lib. ii. sect. i. 24, et lib. xxvii. sect. iii. 

 $ 10. Mascagni, Prodrome della grande anatomia, 

 Firenze, 1819. Hunter John, On certain parts of 

 the animal economy, Lond. 1786. Moreschi Alex. 

 Comment, de urethrae corporis glandisque structura, 

 Mediolani, 1817. Duvernay, in comment. Petro- 

 polit. torn. ii. p. 200. Cuvier, Le9ons d'anatomie 

 comparee, torn. iv. Paris, 1799 1805. Tiedemann, 

 in Journal complementaire, torn. iv. p. 282. 

 Hebenstreit, G. De turgore vitali in Brera Sylloge, 

 torn. ii. Duverney, GEuvres anatomiques, torn. ii. 

 Paris, 1761. Mascagni, P. Hist, vasorum lymphat. 

 sect. ii. Senis, 1787. Beclard, Anat. generate, 

 Paris, 1823. Weber, H. E. Allgemeine anatomic, 

 p. 415. Braunschweig, 1830. Craigie David, M.D. 

 Elements of general and pathological anatomy, 

 Edin. 1828. Muller, in Arcliiv fur Physiologie, 

 Jahr 1835, p. 202. The paper of Professor Muller 

 has been very ably translated in the London Me- 

 dical Gazette, No. 423. 



(J. Hart.) 



EXCRETION. This term is applied to the 

 formation of those fluids in the animal economy, 

 which are destined to no useful purpose in the 

 system, but are intended to be discharged from 

 it, and the retention of which is injurious or 



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