Part 8

The movement of torsion or rotation round its own axis may be proved by the following experiment:--Seated upright, with the back and shoulders well applied against the back of a chair, we can turn the head and neck as far as 70°. Leaning forwards so as to let the dorsal and lumbar vertebræ come into play, we can turn 30° more.

58. =Position and motions of scapula.=--There are a few points worthy of observation about the scapula. It covers the ribs from the second to the seventh inclusive. We can feel its superior angle covered by the trapezius. The inferior angle is covered by the latissimus dorsi, which keeps it well applied against the ribs in the strong and athletic; but in weak and consumptive persons the lower angles of the scapulæ project like wings--hence the term ‘scapulæ alatæ.’

A line drawn horizontally from the spine of the sixth dorsal vertebra over the inferior angle of the scapula gives the upper border of the latissimus dorsi. Another line drawn from the root of the spine of the scapula to the spine of the last dorsal vertebra gives the lower border of the trapezius, which stands a little in relief.

59. The sliding movement of the scapula on the chest can be properly understood only on the living subject. It can move not only upwards and downwards as in shrugging the shoulders--backwards and forwards as in throwing back the shoulders--but it has a rotatory movement round a movable centre. This rotation is seen while the arm is being raised from the horizontal to the vertical position, and is effected by the co-operation of the trapezius with the serratus magnus. The glenoid cavity is thus made to look upwards, the inferior angle slides forwards, and is well held under the latissimus dorsi.

60. For the medical examination of the back, the patient should sit with the arms hanging between his thighs, to lower the scapulæ as much as possible. In this position the spine of the scapula corresponds (nearly) with the fissure between the upper and lower lobes of the lung; the apex of the lower lobe being about the level of the third rib.

THE ABDOMEN.

The student is assumed to be familiar with the conventional lines dividing the abdomen into regions.

61. =Abdominal lines.=--The linea alba, or central line of the abdomen, marks the union of the aponeuroses of the abdominal muscles. It runs from the apex of the ensiform cartilage to the symphysis pubis. As this line is the thinnest and least vascular part of the abdominal wall, we make our incision along it in ovariotomy, and in the high operation of lithotomy; in it, we tap the abdomen in ascites, and the distended bladder in retention of urine.

The so-called ‘linea semilunaris,’ at the outer border of the sheath of the rectus, corresponds with a line, drawn slightly curved (with the concavity towards the linea alba), from the lowest part of the seventh rib to the spine of the pubes. This line would be in an adult about three inches from the umbilicus; but in an abdomen distended by dropsy or other cause, the distance is increased in proportion.

It is important to know the position of the ‘lineæ transversæ,’ or tendinous intersections across the rectus abdominis. There are rarely any below the umbilicus, and generally three above it. The first is about the level of the umbilicus. The second is about four inches higher--that is, about the level of the lowest part of the tenth rib. These are the principal lines, and they divide the upper part of each rectus into two nearly quadrilateral portions, an upper and a lower: of these, those on the right side are a trifle larger than on the left. We see these muscular squares pretty plainly in some athletic subjects. Much more frequently we see them, too much exaggerated, on canvas and in marble. Artists are apt to exaggerate them, and make the front of the belly too much like a chess-board. It is lucky for them that all the world do not see with anatomical eyes.

A familiarity with the shape and position of these divisions of the rectus is of importance, lest we should, in ignorance, make a mistake in our diagnosis. A spasmodic contraction of one of these divisions, particularly the upper, or a collection of matter within its sheath, has been frequently mistaken for deep-seated abdominal disease.

In the erect position, the anterior superior spines of the ilia are a little below the level of the promontory of the sacrum. The bifurcation of the aorta is on about the level of the highest part of the crest of the ilium.

62. =Umbilicus.=--The umbilicus is not midway between the ensiform cartilage and the pubes, but rather nearer to the pubes. In all cases it is situated above the centre of a man’s height. It is a vulgar error to say that when a man lies with legs and arms outstretched, and a circle is drawn round him, the umbilicus lies in the centre of it. This central point is in most persons just above the pubes.

In very corpulent persons two deep transverse furrows run across the abdomen. One runs across the navel and completely conceals it. The other is lower down, just above the fat of the pubes. In tapping the bladder above the pubes in such a case, the trochar should be introduced where this line intersects the linea alba.

Although the position of the umbilicus varies a little in different persons, as the abdomen is unusually protuberant or the reverse, still, as a general rule, it is placed about the level of the body of the third lumbar vertebra. Now, since the aorta divides a little below the middle of the fourth lumbar, it follows that the best place to apply pressure on this great vessel is one inch below the umbilicus, and slightly to the left of it (65). That the aorta can, under favourable circumstances, be compressed under chloroform sufficiently to cure an aneurysm below it, is proved by recorded cases, and by none more effectually than by a case related in the second volume of the ‘Reports of St. Bartholomew’s Hospital.’

It may be asked, why not apply pressure on the aorta above the umbilicus? The answer is, that the aorta above the umbilicus is farther from the surface, and is, moreover, covered by important structures upon which pressure would be dangerous.

63. =Parts behind linea alba.=--Let us next consider what viscera lie immediately behind the linea alba. For two or three fingers’ breadth below the ensiform cartilage there is the left lobe of the liver, which here crosses the middle line. Below the edge of the liver comes the stomach, more or less in contact with the linea alba, according to its degree of distension. In extreme distension the stomach pushes everything out of the way, and occupies all the room between the liver and the umbilicus. When empty and contracted, it retreats behind the liver, and lies flat in front of the pancreas at the back of the abdomen; thus giving rise to the hollow termed the ‘pit of the stomach.’ But as the stomach distends, it makes a considerable fulness where there was a pit. The middle of the transverse colon lies above the umbilicus, occupying space (vertically two or three inches) according to its distension. Behind and below the umbilicus, supposing the bladder contracted, are the small intestines, covered by the great omentum.

64. =Peritoneum.=--The peritoneum is in contact with the linea alba all the way down to the pubes, when the bladder is empty. But when the bladder distends, it raises the peritoneum from the middle line above the pubes; so that with a bladder distended half-way up to the umbilicus, there is a space of nearly two inches above the symphysis where the bladder may be tapped without risk of injury to the peritoneum. For the same reason, we have space sufficient for the successful performance of the high operation for stone. This fact in anatomy must have been well understood by Jean de Dot, the smith at Amsterdam, who, in the seventeenth century, cut himself in the linea alba above the pubes, and took out of his bladder a stone as large as a hen’s egg. The stone, the knife, and the portrait of the operator, may be seen to this day in the museum at Leyden.

65. =Division of Aorta.=--The aorta generally divides at a point one inch and a half below the umbilicus. A more reliable guide to this division than the umbilicus, is a point (a very little to the left) of the middle line about the level of the highest part of the crest of the ilium. A line drawn with a slight curve outwards from this point to the groin, where the pulsation of the common femoral can be distinctly felt (rather nearer to the pubes than the ilium), gives the direction of the common iliac and external iliac arteries. About the first two inches of this line belong to the common iliac, the remainder to the external. Slight pressure readily detects the pulsation of the external iliac above ‘Poupart’s ligament.’

As a rule, the length of the common iliac is about two inches, but it should be remembered there are frequent deviations. It may be between three-quarters of an inch and three inches and a half long. These varieties may arise either from a high division of the aorta, or a low division of the common iliac, or both. It is impossible to ascertain during life what is its length in a given instance, for there is no necessary relation between its length and the height of the stature. It is often short in tall men, and vice versâ. Anatomists generally describe the right as a trifle longer than the left; but their average length is pretty nearly the same.

66. Mr. Abernethy, who in the year 1796 first put a ligature round the external iliac, made his incision in the line of the artery. But the easiest and safest way to reach the vessel is by an incision (recommended in the first instance by Sir Astley Cooper, and now generally adopted), beginning just on the inner side of the artery, a little above Poupart’s ligament, and continued upwards and outwards a little beyond the spine of the ilium. The same incision extended farther in the same direction would reach the common iliac.

67. =Bony prominences.=--The anterior superior spine of the ilium, the spine of the pubes, and the line of Poupart’s ligament, are landmarks with which every surgeon should be thoroughly familiar.

68. =Spine of ilium.=--The spine of the ilium is the spot from which we measure the length of the lower extremity. It is a valuable landmark in determining the nature of injuries to the pelvis and the hip. The thumb easily feels the spine, even in fat persons. Its position with regard to the trochanter major should be carefully examined. The best way to do this is to place the thumbs firmly on the opposite spines, and to grasp the trochanters with the fingers. Any abnormal position on one side is thus easily ascertained with the sound side as a guide.

69. =Spine of pubes.=--The spine of the pubes is the best guide to the external abdominal ring. It cannot easily be felt by placing the finger directly over it, since it is generally covered by fat. To feel it distinctly, we should push up the skin of the scrotum and get beneath the subcutaneous fat. If there be any difficulty in finding it, abduct the thigh, and the tense tendon of the adductor longus will lead up to it.

The position of the spine of the pubes is appealed to as a means of diagnosis in doubt between inguinal and femoral hernia. The spine lies on the outer side of the neck of an inguinal hernia, on the inner side of the neck of a femoral.

The spine of the pubes is nearly on the same horizontal line as the upper part of the trochanter major. In this line, about one full inch external to the spine, is the femoral ring. Here is the seat of stricture in a femoral hernia.

70. =Poupart’s ligament, or crural arch.=--The line of Poupart’s ligament (crural arch) is in most persons indicated by a slight crescent-like furrow along the skin. It corresponds with a line drawn not straight, but with a gentle curve downwards from the spine of the ilium to the spine of the pubes. With the help of the preceding landmarks it is easy to find the exact position of the external and internal abdominal rings, and the direction of the inguinal canal.

71. =Abdominal rings.=--The external abdominal ring is situated immediately above the spine of the pubes. It is an oval opening with the long axis directed obliquely downwards and inwards. Though its size varies a little in different persons, yet as a rule it will admit the end of the little finger, so that we can tell by examination whether it be free or otherwise. To ascertain this, the best way is to push up the thin skin of the scrotum before the finger; then, by tracking the spermatic cord, the finger readily glides over the crest of the pubes and feels the sharp margins of the ring.