INTESTINES. 



fluid. It fcldom contains feces in the adult. Its length, 

 lizc, figure, and direftiou vary greatly : it may be from one 

 to fix long, and from one to three lines broad. It very 

 frequently adiiircs to lli? furrounding parts. 



The rcdtum defecnds in an arched courfe, of which the 

 convexity is turned downwards and backwards, from the 

 laft lumbar vertebra to the aims. Its curve is moll clearly 

 obferved when the part i^ conlidered in a lateral view. Iti 

 the infant, on account of the fmall fi/.c of the pelvis, it is 

 continued for the greatcil part in the abdomen. Its ex- 

 ternal furfacc is unitorm. The peritoneal covering is a par- 

 tial one, and belongs only to the fides and anterior part of 

 the inteftine : behind it is connected to the pelvis by cellular 

 fubftance. This membrane forms two lateral folds, con- 

 tinued, in the male fex, to the fides of the bladder ; in the 

 female to the vagina and the poilerior furface of the broad 

 ligaments of the uterus. From the anterior part of the 

 intelline the peritoneum pades in men to the pofterior and 

 inferior part of the bladder, and in women to the under fur- 

 face of the vagina. Beyond this point the intelline is con- 

 tinued, ftill in a curved courfe, with the gonvexity down- 

 wards, for an inch or more, united by cellular fubllanee in 

 the male fubjccl to the veliculje feminales, in-inarv bladder 

 and proftate, in the female to the vagina. The ferous coat 

 has appendices epiploicas. 



The mufcular covering confifts of a thick and ftrong 

 layer of longitudinal fibres, and of a ilrong ftratum of cir- 

 cular ones : the latter form an oval tumid ring at the end of 

 the gut, called ihe fphinCler ani intcrnus. 



The cellular fubilance is continued, at the end of the gut, 

 into the general fubcutaneous ilratum ; and the mucous 

 lining is gradually, and in the European imperceptibly, lotl 

 in the comraon integuments. But in the negro the bound- 

 ary is more clearly marked by the ceffation of the black 

 rete mucofuni. 



The mucous coat is marked with longitudinal fcrpenline 

 folds, and covered with a copious vifcid mucus: the latter 

 is fecreted by glands, whofe duCts perforate the membrane, 

 and the large'l of which are near the termination of th.e 

 gut. 



The extremity of the intelline is provided with certain 

 muiclcs concerned in the motions perforiricd for the expu!- 

 fion of the feces : thefe arc the levatores ani, fphindler ani, 

 # traufvcrfi perinei, and coccygei. 



The le-valar aiii is a thin, broad, and fiat mufcular plane, of 

 an irregulaily quadrilateral figure, rather curved in its inner 

 furface, and forming a feptum, which clofes the pelvis 

 below, and completes the abdominal cavity. Its origin 

 extends from the pubes to the fpine of the ifchium : it 

 commences by (liort aponeurotic fibres, jnft behind the arch 

 of the former bone, and continues its origin from a broad 

 and thin aponeurofis which covers the obturator internus. 

 The anterior llefhy fibres pafs obliquely downwards, back- 

 wards, and inwards, and arc loll on the prollale and fides 

 of the redlum, where they are intermingled with the 

 fphintler. The larger portion, which is behind thefe, paifes 

 downwards in the lame direclion, is partly united to the 

 oppofite mufcle, by an aponeurotic expanfion, between the 

 reflum and coccyx, and partly fixed to the fide of thj;t 

 bone.. The external furface of the levator is in contact 

 with the obturator interiuis, the gluteus magnus, the tranf- 

 verfus perinei, and lower dovk-n with a large quantity of 

 cellular and adipous tiffue. The inner furface corrcfponds 

 to the proftate, bladder, and reclum. For the defcription 

 of the coccygeus, fee CocC¥G.=kus. 



T\w fphinSer ani furrounds the termination of the intelline 

 juil under the integuments, and is comnwnly divided into 



the fphinfter cutaneus, or externus, and the interr.us. The 

 latter, as we have already mentioned, is to be regarded ra- 

 ther as the termination of the circular mufcular fibres of 

 the put, than as a dillincl mufcle. It is a pretty thick 

 mufcular ring, about half an inch in breadth. Externally, 

 the longitudinal mufcular fibres of the rcftum cover it : on 

 the infide it covers the mucous membrane of the intelline. 

 The fuperior margin is continuous v.ith the circular fibres 

 of the gut : the inferior is placed betvvcen the opening of 

 the external fphindler and the membrane of the inteftinc. 



The fphinfter externus, or cutancus, is placed more fuper- 

 ficially than the former, and extends from the apex of the 

 coccyx to the poilerior part of the pcnncum. It is flat- 

 tened, elliptical, with its long axis incUned from behind 

 forwards, and perforated in the middle. We diftinguilh in 

 it a fuperior and an inferior furface, a right and left edge, 

 and an anterior and pofterior extremity. The thin (kin fi'.r- 

 rounding the anus covers the under furface : the upper cor- 

 refponds to the levator ani, being at firll Icparated from it 

 by cellular tiffue, but having its fibres completely blended 

 with thofe of that mufcle on the reftum. The iront end 

 forms a fliarp point, extending more or lefs under the back 

 edge of the accelerator urinse, to which, as well as to the 

 tranfverfi perinei, it is clofely connetled. The pofterior 

 extremity is alfo pointed, and attached to the coccyx by a 

 denfe cellular matter approaching to the nature of liga- 

 ment. The margins are partly covered by the fltin, and 

 partly by a mafs of cellular and adipous fubilance. 



The fphinCler confifts wholly of flclhy fibres, which de- 

 fcribe concentric arcs of circles : thofe of the two fides 

 are united at acute angles before and behind the anus. 



The front end of the mufcle is lefs elongated and acute 

 in the female thun in the male fuhj -ft. In bctli its fibres 

 are intimately blended with tliofe of the internal fphincler. 



The tranfivr/its pmitui is fituatcd towards the b^ck part 

 of the perineum, between the tuberofity and rami:s of the 

 ifchium, and the middle of the fpace comprifed between 

 the bulb of the urethra and the anus. It is thin, flat- 

 tened, and fomewhat triangular. The anterior furface is 

 inclined downward?, and correfponds to the eredor penis 

 and accelerator, and to the fat which fills the intervals be- 

 tween thefe. The pofterior, inclined upw.-.rds, lies againd 

 the levator ani : celltilar tiflue, and the deepfeatcd branch 

 of the internal pudic artery, fepnratc thcni. The outer edge 

 is attached to the inner furface of the tubcrcfity and ramu.i 

 of the ifchium, above the ercClor penis and the root of the 

 crus penis. The inner edge is united to that of the oppo- 

 fite mufcle, to the front of the fphinfter ani, and to the 

 back edge of the accelerator. The tranfverfus is feparated 

 from the flcin in front by a confidcrahle quantity of fat : 

 behind it is confounded with the reddifli cellular tiffue 

 found in the angle between the bulb of the urethra, and 

 the root of the corpus cavernofum. The origin is aponeu- 

 rotic ; and the termination is ufually in a tendinous line. 



T\k Iranfiierfiis periiin alter is not conftantly found. It 

 is a flendcr elongated fafcicuhts, running parallel to the 

 ifchium, on the inner edge of the ereftor penis. The 

 origin is derived from the tuberofity of the bone, near to 

 that of the erector ; it terminates above in a thin apt neu- 

 rofis connefted to the bulb of the urethra, or corpus caver- 

 nofum. 



Motions performed by thefe Mifks.— The mufcidar or- 

 gans juft defcribed have two principal offices : i They 

 move the whole pelvic vifcera together. 2. They aft on 

 the reftum in particular. The levator and coccygeus are 

 principally concerned in the former cafe. They rcprcfent 

 amufcular plane capable of elevation and deprelTion, and b{ 



mOviiiK 



