A system of practical medicine. By American authors. Vol. 2

by Unknown

FIG. 3.

Diagram showing the course of the vaso-motor nerves of the liver, according to Cyon and Aladoff. These nerves are indicated by the dotted line which accompanies them: a, vaso-motor centre; b, trunk of the vagus; c, passage of the hepatic vaso-motor nerves from the cord along the vertebral artery; d, fibres going on each side of the subclavian artery and forming the annulus of Vieussens; e, first dorsal ganglion; f, ganglionated cord of the sympathetic; g, the spinal cord; h, the splanchnic nerves; i, coeliac ganglion, from which vaso-motor nerves pass to the hepatic and intestinal vessels; k, the lungs, to which fibres of the vagus are seen distributed; l, the liver; m, the intestine; n, the arch of the aorta.

I say, by branches of the sympathetic not precisely determined, because our power to produce artificial diabetes fails below the first thoracic ganglion; for section of the sympathetic between the tenth and twelfth ribs, and of the splanchnics, is not followed by glycosuria, although the vaso-motor nerves to the liver are known to pass through them.

According to Eckhard,³ the phenomena of artificial glycosuria are irritative and not paralytic. This view he believes sustained by his own experiments, according to which if the splanchnics, through which the vaso-motor nerves of the liver pass, are cut prior to the diabetic puncture, not only does this operation fail to produce glycosuria, but it even renders ineffectual the puncture itself as well as the section higher up. But Cyon and Aladoff remind us that it is not mere dilatation of the hepatic vessels, but increased velocity in the movement of the blood, which deranges the sugar-assimilating function and causes glucose to appear in the urine. The vaso-motor nerves of the intestinal blood-vessels also pass through the lower part of the sympathetic and the splanchnics, and section of the latter must cause these blood-vessels to dilate. Now, in rabbits, in which this experiment is usually performed, the digestive canal is very long, and the blood-vessels so capacious that when dilated they hold as much blood as all the rest of the vascular system together, so that when the lower sympathetic and splanchnics are cut, so much blood goes into the intestines that the increased velocity required in the blood-vessels of the liver to produce glycosuria is impossible. But if the vessels of the liver be first dilated by puncturing the floor of the fourth ventricle, section of the sympathetic or of the splanchnics may then be made without arresting the formation of sugar; whence it would appear that the glycogenic influence may still pass through the lower sympathetic and splanchnics.

³ Beiträge zur Anat. und Physiologie, iv., 1859, p. 1; vii., 1873.

In view of the fact that Eckhard⁴ has failed to confirm the results of Cyon and Aladoff, but has traced the glycogenic influence down the spinal cord as far as the fourth dorsal vertebra in rabbits, and even a little lower, and that Schiff⁵ has shown that diabetes sometimes results after section of the anterior columns of the cord between the medulla and the fourth cervical vertebra, Dr. Brunton⁶ suggests that the vaso-motor nerves of the liver may not always leave the spinal cord to join the sympathetic by the branches accompanying the vertebral artery, but sometimes pass farther down the cord, leaving it by the communicating branches to some of the dorsal ganglia, as indicated in Fig. 4.

⁴ Beiträge zur Anat. u. Physiologie, viii., 1877, p. 79.

⁵ Untersuchungen über Zuckerbildung in der Leber, 1859, S. 108.

⁶ Lectures on the Pathology and Treatment of Diabetes Mellitus; reprinted from the British Medical Journal, 1874, p. 12.

FIG. 4.

Diagram showing another course which the vaso-motor nerves of the liver may take. The letters indicate the same parts as in Fig. 3. The hepatic vaso-motor nerves are here represented as passing lower down the cord than in Fig. 3, and leaving it by communicating branches to the second dorsal ganglion. It is possible that they may sometimes leave by the branches to the first, and sometimes by those going to a lower, ganglion. In such cases any irritation to the third or one of the other cervical ganglia may cause diabetes by being conveyed along the vertebral artery and up the cord, as indicated by the dark line, to the vaso-motor centre, where it may cause reflex inhibition in the same way as any irritation to the vagus.