ANUS. 



175 



quantity and consistence of the adipose substance 

 found in this region vary considerably in dif- 

 ferent individuals at the several periods of life, 

 and under various conditions of health ; a fact 

 most important for the surgeon to bear in mind, 

 inasmuch as this diversity causes corresponding 

 differences in the physical characters which this 

 region presents under these particular circum- 

 stances. In children, and in the female, in youth 

 and middle age, as also in the robust and 

 healthy male, this region will be found plump, 

 or convex around the anus, whereas in the ema- 

 ciated, the sickly, or the old, it often presents the 

 very opposite appearances; and a proportional 

 difference may be observed in the depth of the 

 perinaeum, or in the distance between the neck 

 of the bladder and the surface : the greatest 

 extremes of this difference have been found 

 between two and four inches, a circumstance 

 which bears materially on the lateral operation 

 of lithotomy. 



So much of the Rectum as lies beneath the 

 cul de sac of the peritoneum, may be consi- 

 dered as appertaining to the anal region, and 

 must, therefore, be noticed at present ; below 

 the reflection of that membrane, this intestine 

 descends obliquely forwards between the sacrum 

 and bladder, in the male as far as the prostate 

 gland, and in the female as far as the vagina ; 

 it is there on a level with the inferior extremity 

 of the coccyx, and then it bends downwards 

 and backwards, and ends in the anal opening ; 

 the perinaeal portion of the Rectum, therefore, 

 is convex forwards and concave towards the 

 coccyx ; hence in introducing into this intestine 

 the bougie, enema pipe, or even the finger, it 

 should be directed at first upwards, and for- 

 wards, and then upwards and backwards : in 

 the child, however, this precaution is not ne- 

 cessary, as the course of this intestine is not so 

 much curved, the name of Rectum being then 

 more correctly applied than in the adult. 



In order to examine the several parts con- 

 tained in the anal region, the thighs should be 

 fully separated, flexed, and fixed on the pelvis; 

 the first object which attracts attention is the 

 Anus. 



This opening is situated in the median line, 

 at the bottom as it were of a deep excavation, 

 which is bounded on either side by the tube- 

 rosity of the ischium, with the superincumbent 

 muscular and adipose substance ; in the erect 

 position it appears at a great depth from the 

 surface, in consequence of the approximation 

 of the nates. In the adult the anus is from one 

 inch to an inch and a half distant from the 

 point of the coccyx, and three inches from the 

 arch of the pubis; it is in some measure, but 

 not perfectly, fixed in its situation, anteriorly 

 by an indirect attachment to the interosseous 

 or triangular ligament of the urethra, and pos- 

 teriorly by a dense fibrous tissue, which forms 

 a sort of raphe between it and the coccyx, and 

 to which the muscles and integuments adhere. 

 In the natural and healthy state, the anus pre- 

 sents the appearance of a small rounded, or 

 rather elliptical orifice, whose border is thrown 

 into numerous small plaits, or rugae, which 

 during the extended state of the opening are 



effaced ; these rugae are occasionally so deep as 

 to admit of the escape of a small quantity of 

 fluid. As the skin approaches the margin of 

 this opening it becomes very fine and delicate, 

 is gathered into those several radiated folds or 

 plaits, which sink into it, and in the same man- 

 ner as at the other outlets of the body, it be- 

 comes continuous with the lining mucous mem- 

 brane of the intestine, there being no exact line 

 of demarcation, except that of an increased 

 vascularity, to distinguish the one from the other. 

 This plaited condition of the skin which lines 

 this opening arises from the close contraction 

 of the subjacent muscle, and is doubtless de- 

 signed to admit of the more easy dilatability 

 of the anus during defecation ; this opening, 

 however, is never equal to the diameter of the 

 rectum at a little distance above it. In the 

 child the integument surrounding the anus is 

 smooth and red, in the adult it is of a deep 

 brown colour and studded with several fine 

 hairs, which, however, are usually absent in the 

 female. In this situation also the cutaneous 

 follicles are very distinct and numerous, but 

 not so prominent as in the scrotum ; they secrete 

 a mucous or sebaceous matter which gives to 

 the skin a shining or oily appearance, and 

 adapts it to the functions of the part: from the 

 absence or from the vitiated condition of this 

 secretion, painful and troublesome excoriations 

 not unfrequently ensue. In the healthily state 

 the margin of the anus feels firm and resisting, 

 and together with the surrounding muscles 

 forms a floor or support to the inferior part of 

 the pelvis, in the centre of which floor the 

 rectum and its contents are maintained, and 

 on either side a mass of cellular and adipose 

 substance. 



Muscles. The muscular apparatus connected 

 with the lower extremity of the rectum consists 

 of the superficial and the deep sphincters of 

 the anus, also the right and left levatores ani, 

 to which may be added the two transversi 

 perincei, and the two coccygcei muscles. 



The first two, namely, the sphincter muscles, 

 surround the anus, and may be regarded as a 

 modification, or as a particular development of 

 the general circular muscular tunic, which is 

 continued around the whole alimentary tube 

 from the mouth to the anus, and which in dif- 

 ferent situations exhibits a considerable increase 

 in colour and consistence, for example, in the 

 lips, around the fauces, the oesophagus, the 

 pylorus, &c. The name of these muscles in- 

 dicates their principal function, while the other 

 muscles which have been alluded to proceed from 

 certain fixed points to be inserted into the lower 

 extremity of the rectum, and must, therefore, 

 rather serve to retain the anus in its situation 

 or to restore it to its natural condition, when 

 in the exercise of its functions it has been con- 

 siderably dilated, or slightly displaced by the 

 expulsive efforts of the diaphragm and abdo-- 

 minal muscles. We shall first examine the 

 descriptive anatomy of these individual muscles, 

 and then consider their several powers or pur- 

 poses in the economy of the surrounding organs. 

 Although there are two sphincter muscles of the 

 anus, yet this name is generally applied to the 



