The internal sphincter is a collection of the circular fibres of the muscular coat of the bowel, about five-eighths of an inch in width, and constitutes in reality the terminus of the gut. For the external sphincter is a thin band of distinct and separate muscular fibres, elliptical in shape, between three and four inches from its anterior to its posterior extremity, and expands out around the margin of the anus like the flaring end of a trumpet; with its superficial layer in close relation to the skin which it draws down in radiating folds.
With this understanding of the anatomical relations, it will be seen that the external muscle contributes so slightly to the length of the canal, that it might be considered wholly on the outside, where it guards closely the entrance, and is nowise concerned in an examination with a speculum except as a feature of incumbrance.
To correct an erroneous idea that there is any considerable depression or space intervening between the muscles, we mean, when we say between the sphincters, the distance bounded by the fibrous ring uniting the two muscles below, and the upper portion of the internal muscle above. More simplified, we mean all the surface included between the upper margin of the internal sphincter and its junction with the external muscle at the anal verge.
All examinations with a speculum should be preceded by an enema of warm water to wash away the mucous and retained feces in and about the sphincters. Let the patient lie on either side, turning partially on the chest, with knees drawn up, the one uppermost more firmly flexed on the abdomen, and hips so elevated that the speculum, when introduced points or inclines downward, and admits of strong natural light to fall in parallel rays to its axis.
Warm the speculum by dry heat over a single blast kerosene stove, where gas is not convenient. A suitable kerosene stove is an indispensible adjunct to an office for heating instruments, water, etc., causing no smell and leaving no deposit of sut on the bottom of vessels as done by gas or alcohol. Use white vaseline as a lubricant; everything that tends to whiteness helps the sight. The vaseline may be squeezed from a tin-foil tube, and the finger not soiled in preparing the speculum for insertion.
Fig. 13.—A suitable Kerosene Stove for office use. It is clean, safe, cheap, portable and has perfect combustion.
To prevent the loose tissue from rolling up and being pushed in with the speculum, the patient may assist by holding the upper buttock away, while the physician introduces the instrument with one hand and retracts the opposite buttock with the other.
Introduce slowly, giving time for the muscles to relax, bearing in mind that all movements about the rectum and anus must be extremely easy and gentle. The proximal end of the slot must be carried and kept above the external sphincter during the entire course of the examination. It matters not what kind of a speculum is being used, the value of the instrument will greatly depend upon its power to hold this muscle out of the way.
A closed end speculum, with a proportionate slot and smooth corners, can be slowly rotated without any difficulty where the mucous membrane is not very loose and baggy and no prominences in the route. But if a hemorrhoid be in the way it will immediately drop in the slot and further progress is thus impeded.