173 



ANUS. 



neal). This pair of small muscles extends 

 in a direction nearly parallel to the ante- 

 rior border of the anal region ; each arises 

 from the inside of the tuber ischii, passes 

 inwards, forwards, and downwards to join its 

 fellow in the median line of the perinaeum, 

 where it is also partially attached to the cuta- 

 neous sphincter of the anus, and to the acce- 

 leratores urinae muscles, or in the female to the 

 constrictor vaginae. These muscles are very 

 unequal in appearance in different subjects ; 

 in some they are feeble and indistinct, in others 

 very strong, and sometimes divided into two 

 on one or both sides, the additional or minor 

 muscle being superior and anterior. In the 

 female these muscles are often found more dis- 

 tinct than in the male, but even here much 

 variety exists ; in many subjects they appear 

 to be simply composed of some of the anterior 

 and partially detached fibres of the middle 

 portions of the levatores ani imiscles. The 

 transversi perinaei muscles form the bases of 

 the two lateral triangular regions contained in 

 the anterior or urethral perinaeum, and one 

 of them, the left, is necessarily divided in 

 the lateral operation for lithotomy; they are 

 surrounded by much adipose matter ; two arte- 

 ries, both branches of the internal pudic, take 

 a course parallel to them, viz., the super- 

 ficial transverse perinaeal, and the deep trans- 

 verse, or the artery of the bulb. These muscles 

 are enveloped between the layers of the perinaeal 

 fasciae. The superficial layer, which is continu- 

 ous with the Ischio-rectal, covers them in their 

 course forwards to the urethral muscles, and 

 the deep layer, or the triangular ligament of 

 the urethra, which is continuous with the ex- 

 ternal or Ischiatic layer or obturator fascia, lies 

 between them and the pelvis. These muscles, 

 therefore, will have the effect of making tense 

 the different perinaeal aponeuroses, and thus 

 they can support, strengthen, and compress 

 generally the parts in the perinseum ; they can 

 also compress, and thus assist in clearing the 

 orifice of the anus, at the same time that they 

 draw back and raise this part, somewhat in 

 the same manner as the levatores ani muscles. 

 According to some anatomists these muscles 

 are considered as dilators of the bulb of the 

 urethra, as well as of the vagina ; but it is more 

 than doubtful whether they can exert any such 

 action. When these muscles are divided, the 

 base of the deep perinseal fascia, or triangular 

 ligament of the urethra, is exposed. This will 

 be observed to have some influence in main- 

 taining the rectum and anus in their situation ; 

 its posterior border, being attached to the 

 levatores ani muscles, and to the bulb of the 

 urethra, serves to maintain a close connection 

 between these parts, which is still further ef- 

 fected by the interlacement of the muscles of 

 the anus with those which cover the bulb. 

 (See PERINEUM.) 



Levatores ani (sous-pubio-coccygien).1\\is 

 pair of broad, thin, flat, and nearly square 

 muscles form a septum somewhat broader 

 above than below, between the pelvis and 

 perinaeum, which, together with the aponeu- 

 roses covering its upper and lower surfaces, 



and with the coccygeal muscles and the trian- 

 gular ligament of the urethra, completely in- 

 tercepts all communication between these two 

 regions except through the natural passages 

 for the urethra, vagina, and rectum. Although 

 these muscles are described as two, there ap- 

 pears no good reason for the division, for the 

 fibres of opposite sides have a common in- 

 sertion, partly into the circumference of the 

 rectum and partly into a middle cellulo-ten- 

 dinous raphe before and behind that intestine. 

 It appears more correct to considerthese muscles 

 as one circular muscular septum extended across 

 and within the lower opening of the pelvis, 

 concave towards this cavity, and convex to- 

 wards the perinseum.. The fibres attached by 

 their circumference to the interior of the pelvis, 

 and converging thence towards the median line 

 of the perinaeum, are inserted into and around 

 the rectum ; in fact the muscle resembles the 

 diaphragm in form, in the circumference being 

 its origin or fixed attachment, and the central 

 portion being its insertion, also in its being 

 perforated for the transmission of certain parts ; 

 the analogy only fails in the absence of a 

 central tendon, and in the fibres being prin- 

 cipally inserted into the parts passing through 

 it. The fact, however, of there being an inter- 

 ruption in the origin of this muscle in the 

 middle line both before and behind, in which 

 respect again there is a resemblance to the 

 sternal and vertebral deficiences in the dia- 

 phragm, is the cause of its being described as 

 consisting of a right and left muscle, which dis- 

 tinction, it should be observed, is only an 

 artificial one, for during life the fibres of both 

 sides act together, and in all respects constitute 

 but a single muscle. 



The origin of the levator ani muscle may be 

 exposed by tearing the peritonaeum from the 

 parietes of the pelvis, together with a con- 

 siderable quantity of loose cellulo-adipose 

 membrane. The recto-vesical layer of the pel- 

 vic fascia should then be divided near to the 

 neck and sides of the bladder, and carefully 

 raised towards the wall of the pelvis. The 

 muscle will then be seen to arise on each side 

 by three attachments, which, however, form one 

 continuous semicircular line extending from 

 the pubis to the spine of the Ischium ; its 

 anterior portion is attached to the back part of 

 the pubis, a little above its arch, and imme- 

 diately below the anterior vesical ligaments by 

 short aponeurotic fibres commencing a little 

 distance from the symphysis, and extending 

 outwards as far as the notch in the thyroid 

 hole ; its second or middle attachment is to 

 a strong tendinous arch, which extends from 

 the pubis to the spine of the Ischium, and 

 which is formed at the separation or junction 

 of the pelvic fascia into its superior or recto- 

 vesical layer, and its inferior or perinaeal layer ; 

 its third or posterior attachment is to the spinous 

 process of the ischium. All the fibres pass 

 downwards and towards the median line to 

 their insertion ; the inferior border of this 

 muscle is shorter but thicker than the superior. 

 The fibres of the first, or pubal portion, des- 

 cend a little obliquely backward^ on each side 



