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.