AORTA. 



187 



the integuments, or in both these directions, 

 it continues to secrete and to discharge a con- 

 siderable quantity, and shews no disposition to 

 alter its action or to heal. We have already 

 detailed all the local peculiarities of the ischio- 

 rectal region (the seat of this abscess) which 

 can satisfactorily explain the difficulty or the 

 impossibility of keeping at rest or retaining in 

 apposition the sides of the cavity, a condition 

 almost essential to the healing of an abscess in 

 any situation, and hence the necessity of sur- 

 gical interference. Abscess in this region 

 frequently originates close to the rectum in 

 consequence of irritation and ulceration in this 

 intestine; this irritation may be caused by 

 disease, such as cancer or stricture of the 

 rectum, or by some foreign body becoming 

 impacted in one of the lacunae. Above the 

 sphincter is the rectal pouch, and an irre- 

 gularly shaped or sharp substance, such as a 

 pin, a fish-bone, or one of the small bones of 

 a fowl, &c. brought into this in the fcecal mass, 

 may catch in its villous or rugous surface, the 

 muscular powers of the intestine are excited 

 by this irritation to increased and repeated 

 efforts of expulsion ; these only serve to im- 

 pact more closely the foreign body in the 

 parietes of the intestine ; the submucous tissue, 

 which may now contain the whole or part of 

 this substance, becomes inflamed, suppuration 

 follows, an abscess is formed close to the intes- 

 tine; in some time the matter is discharged 

 either through the rectum and anus, or coming 

 to the surface of the nates it receives exit by 

 puncture. In this case of abscess, which we 

 suppose to have been caused by a foreign body 

 impacted in the intestine, the matter is usu- 

 ally discharged by the rectum, at least at first, 

 although this exit will not always prevent it 

 still tending towards the cutaneous surface : 

 in cases of fistula, however, arising from such 

 a cause, we are most likely to meet with the 

 blind internal fistula, at least in the early 

 period; whereas, when abscess forms spon- 

 taneously in this region, and opens on the 

 surface, the intestine is often at first and for 

 some time wholly disengaged from the disease, 

 even after the abscess has opened, notwith- 

 standing which it is productive of great in- 

 convenience and more or less of pain during 

 defaecation ; in this state, when the fistula or 

 abscess remains discharging through the skin 

 only, it constitutes what is termed a blind 

 external fistula ; by degrees the rectum be- 

 comes denuded, and ultimately ulceration 

 opens it by one, and sometimes, but rarely, 

 by more orifices ; this opening is usually about 

 half an inch above the edge of the anus, and 

 between the two sphincters. I have observed 

 it to hold this situation in a great number of 

 cases, which I have examined both in the 

 living and the dead ; in a few instances, how- 

 ever, I have found it opening at a higher point. 

 When the abscess arises from irritation in the 

 rectum, then I have observed the internal 

 opening to be higher, that is, in the dilated 

 pouch of the rectum, which during life will 

 appear to be from an inch and a half to two 

 inches from the anus; but when the abscess 



has commenced spontaneously in the anal 

 adeps, and opened on the surface first, I have 

 then in general found the rectal opening less 

 than an inch distant from the anal orifice, and 

 in a groove or recess between the two sphinc- 

 ters. When the abscess discharges by two 

 openings, that is, through the skin and through 

 the rectum, a perfect or complete fistula is then 

 said to exist. 



Fistulae occasionally appear in the anal region 

 which have their source at a much greater dis- 

 tance ; thus, any diseases of the uterus or 

 vagina in the female, of the prostate or urethra 

 in the male, which end in suppuration, may 

 cause collections of pus which will burrow 

 under the fasciae and skin to the vicinity of 

 the anus, and open near it or even into the 

 rectum. Psoas and lumbar abscesses also may 

 descend into the pelvis and approach the sur- 

 face, either in front or at one side of the anus. 

 In morbus coxae also chronic abscesses which 

 form about the nates not unfrequently open in 

 the same situation. 



Polypus is seldom a disease of the anus; it 

 most usually grows from the rectum, and pro- 

 trudes occasionally only at the anus. 



(Robert Harrison.) 



For the Bibliography of this article see that 

 of INTESTINAL CANAL. 



AORTA* (human anatomy). (Arteria 

 magna. Fr. aorte. Germ. Aorta, die grosse 

 Schlagader. Gr. ao^-ni.) Hippocrates applied 

 the term ao^rai to the lower part of the bronchi. 

 Aristotle called the great trunk of the arterial 

 system pAeiJ' TJ. 



The aorta, one of the two great arteries 

 which spring from the heart, is the trunk of the 

 arterial system of the general circulation; it 

 arises from the extreme right part of the base 

 of the left ventricle of the heart, which, from 

 this circumstance, is sometimes called the 

 aortic ventricle. There is a ring of tendinous 

 structure surrounding the aortic opening of the 

 ventricle, which in the stag and some others of 

 the ruminantia is more or less partially ossified; 

 into this ring the muscular fibres of the heart 

 are inserted. The middle tunic of the aorta 

 is divided at its commencement into three 

 semicircular flaps by an equal number of angu- 

 lar notches, forming thus a festooned edge 

 which is bordered throughout its whole extent 

 by a marginal tendinous cord. These three 

 semicircular flaps touch the aortic opening of 



* The etymology of this term is by no means 

 clear. The following extract from Spigelius (de 

 corp. hum. fabrica) gives a not improbable origin 

 for it. "Veteribus Graecis opTv dictam fuisse 

 vaginam cultrorum Macedonibus familiarem, quo- 

 rum manubrium nonnihil incurvatum erat, ad quam 

 sane figuram quam proxime accedere videtur arte- 

 rize magnae t'uncus, qua parte ex corde onginem 

 suam ducit." Cloquet suggests the theme, aoprso/uat, 

 suspendor, " parceque 1'aorte consideree ^dans sa 

 t >talite parait comme suspendue au cceur." Aris- 

 totle, by whom the term seems to have been first 

 employed, generally denominated it <f>Xg4- tha.'rrw, 

 in reference to the vena cava, which he considered 

 the greater vein. R. B. T. 



