a living animal, and measures the outflow per unit of time. An increase in the outflow means a dilatation of the vessels, diminution means constriction. He finds that the outflow diminishes in the rabbit when the vagus is stimulated in the neck, and increases when the cervical sympathetic is stimulated. Franck measures the pressure simultaneously in the pulmonary artery and left auricle, a method apparently also trustworthy. The stimulation of the inner surface of the aorta causes a rise of pressure in the pulmonary artery and a simultaneous fall in the left auricle, indicating, according to Franck, the vaso-constrictor power of the sympathetic nerve over the pulmonary vessels. A reflex constriction is also produced by the stimulation of the central end of a branch of the sciatic, intercostal, abdominal pneumogastric, and abdominal sympathetic nerves (see Fig. 45).

Heart.-Vaso-motor fibres for the coronary arteries of the heart have been

described.1

Intestines.-The mesenteric vessels receive vaso-constrictor fibres from the sympathetic chiefly through the splanchnic nerve. The vaso-constrictors of

the jejunum, as a rule, begin to be found in the rami of the fifth dorsal nerves; a little lower down, those for the ileum come off; and still lower down, those for the colon; none arise below the second lumbar pair. According to Hallion and Franck, vaso-dilator fibres are present in the same sympathetic nerves that contain vaso-constrictors. The dilator fibres are most abundant or most powerful in the rami of the last three dorsal and first two lumbar nerves. There is some evidence of the presence of vaso-dilator fibres in the vagus. The excitation of the vaso-constrictor centres by the blood in asphyxia produces constriction of the abdominal vessels. The vaso-dilator as well as the vaso-constrictor fibres of the splanchnic probably end in the solar and renal plexuses.

3

Liver.-Cavazzani and Manca have recently attempted to show the presence of vaso-motor fibres in the liver. Their method consists in passing warm normal saline solution from a Mariotte's flask at a pressure of 8 to 10 millimeters Hg through the hepatic branches of the portal vein and measuring the outflow in a unit of time from the ascending vena cava. On stimulating the splanchnic nerve they observed that the outflow was usually diminished though sometimes increased, indicating perhaps that the splanchnics contain both vaso-constrictor and vaso-dilator fibres for the hepatic branches of the portal vein. The vagus appeared to contain vaso-dilator fibres. Further studies are necessary, however, before pronouncing definitely upon these questions.

1 Porter: Boston Medical and Surgical Journal, 1896, cxxxiv. 39; Porter and Beyer: American Journal of Physiology, 1900, iii. p. xxiv.; Maass: Archiv für die gesammte Physiologie, 1899, lxxiv. p. 281.

* Hallion and Franck: Archives de Physiologie, 1896, xxviii. pp. 478, 493; Bunch: Journal of Physiology, 1899, xxiv. p. 72.

* Cavazzani and Manca: Archives italiennes de Biologie, 1895, xxiv. p. 33; François-Franck and Hallion: Archives de Physiologie, 1896, pp. 908, 923; 1897, pp. 434, 448.

Kidney. The vaso-motor nerves of the kidney leave the cord from the sixth dorsal to the second lumbar nerve. In the dog, most of the renal vasomotor fibres are found in the eleventh, twelfth, and thirteenth dorsal nerves. The stimulation of the nerves entering the hilus of the kidney between the artery and vein causes a marked and sudden renal contraction, but the organ soon regains its former volume. Constriction follows also the stimulation of the peripheral end of the cut splanchnic nerve. Bradford has demonstrated renal vaso-dilator fibres for certain nerves by stimulating at the rate of one induction shock per second. For example, the excitation of the thirteenth dorsal nerve with 50 to 5 induction shocks per second gave always a constriction of the kidney, but when a single shock per second was employed, the kidney dilated. If the cells connected with the renal vaso-motor fibres are stimulated directly by venous blood as in asphyxia, the animal being curarized,. a decided constriction of the kidney results. The reflex excitation of these cells is of especial importance. The stimulation of the central end of the sciatic or the splanchnic nerves causes renal constriction. The same effect is easily produced by stimulating the skin, for example, by the application of cold. The stimulation of the sole of the foot in a curarized dog caused contraction of the renal vessels. There is some evidence that the splanchnic vaso-motor fibres for the kidney end in the cells of the renal plexus.

Spleen. The stimulation of the peripheral end of the splanchnic nerves causes a sudden and large diminution in the volume of the spleen. It is, however, not certain whether the constriction of the spleen is to be referred primarily to a constriction of its blood-vessels or to the contraction of the intrinsic muscular fibres which play so large a part in the changes of volume of this organ. The doubt is strengthened by the fact that section of the splanchnic nerves does not alter the volume of the spleen; dilatation would be expected were these nerves the pathway of vaso-constrictor fibres for the spleen.

Pancreas.-François-Franck and Hallion find vaso-constrictor fibres in the sympathetic chain between the sixth and eleventh ribs; they leave the spinal cord from the fifth dorsal to the second lumbar ramus communicans, pass into the greater and lesser splanchnic nerves, and reach the gland along the pancreatic artery. A few dilator fibres were found in the sympathetic; more in the the vagus.3

External Generative Organs.—The recent history of the vaso-motor nerves of the external generative organs-namely, those developed from the urogenital sinus and the skin surrounding the urogenital opening-begins with Eck1 Wertheimer: Archives de Physiologie, 1894, p. 308; Bayliss and Bradford: Journal of Physiology, 1894, xvi. p. 17.

Schäfer and Moore: Journal of Physiology, 1896, xx. p. 1.

3 Franck and Hallion: Archives de Physiologie, 1896, pp. 908, 923.

Franck: Archives de Physiologie, 1895, p. 122; Langley and Anderson: Journal of Physi-. ology, 1895, xix. p. 76.

hard, who showed that the stimulation of certain branches of the first and second, and occasionally the third, sacral nerves (dog) caused a dilatation of the blood-vessels of the penis and erection of that organ, and with Goltz, who found an erection centre in the lumbo-sacral cord. Numerous researches in recent years, among which the reader is referred especially to the work of Langley and Langley and Anderson, have shown that the vaso-motor nerves of the external generative organs of both sexes may be divided into a lumbar and a sacral group.

The lumbar fibres pass out of the cord in the anterior roots of the second, third, fourth, and fifth lumbar nerves, and run in the white rami communicantes to the sympathetic chain, from which they reach the periphery either by way of the pudic nerves or by the pelvic plexus. The greater number take the former course, running down the sympathetic chain to the sacral ganglia, and passing from these ganglia through the gray rami communicantes to the sacral nerves. None of the fibres thus derived enter the nervi erigentes of Eckhard. Of the various branches of the pudic nerves (rabbit), the nervus dorsalis causes constriction of the blood-vessels of the penis and the perineal nerve contraction of the blood-vessels of the scrotum. The course by way of the pelvic plexus is taken by relatively few fibres. They run for the most part in the hypogastric nerves, a few sometimes joining the plexus from the lower lumbar or upper sacral sympathetic chain, or from the aortic plexus. The presence of vaso-dilator fibres in the lumbar group is disputed.

The sacral group of nerves leave the spinal cord in the sacral nerve roots. Their stimulation causes dilatation of the vessels of the penis and vulva.

Internal Generative Organs (those developed from the Müllerian or the Wolffian ducts).-Langley and Anderson find vaso-constrictor fibres for the Fallopian tubes, uterus, and vagina in the female, and the vasa deferentia and seminal vesicles in the male, in the second, third, fourth, and fifth lumbar nerves. The internal generative organs receive no afferent, and probably no efferent, fibres from the sacral nerves.

The position of the sympathetic ganglion-cells, the processes of which carry to their peripheral distribution the efferent impulses brought to them by the efferent vaso-motor fibres of the spinal cord, may be determined by the nicotin method of Langley. About 10 milligrams of nicotin injected into a vein of a cat prevent for a time, according to Langley,' any passage of nerve-impulses through a sympathetic cell. Painting the ganglion with a brush dipped in nicotin solution has a similar effect. The fibres peripheral to the cell, on the contrary, are not paralyzed by nicotin. Now, after the injection of nicotin the stimulation of the lumbar nerves in the spinal canal has no effect on the vessels of the generative organs. Hence all the vaso-motor fibres of the lumbar

nerves must be connected with nerve-cells somewhere on their course. The lumbar fibres which run outward to the inferior mesenteric ganglia are for the most part connected with the cells of these ganglia. A lesser number is con1 Langley and Anderson: Journal of Physiology, 1894, xvi. p. 420.

nected with small ganglia lying as a rule near the organs to which the nerves are distributed. The remaining division of lumbar fibres running downward in the sympathetic chain, and including the majority of the nerve-fibres to the external generative organs are connected with nerve-cells in the sacral ganglia of the sympathetic.

The sacral group of nerves enter ganglion-cells scattered on their course, most of the nerve-cells for any one organ being in ganglia near that organ. Bladder.-Neither lumbar nor sacral nerves send vaso-motor fibres to the vessels of the bladder.

Portal System.-It has already been said that vaso-constrictor fibres for the portal vein were discovered by Mall in the splanchnic nerve. Constrictor fibres have been found by Bayliss and Starling in the nerve-roots from the third to the eleventh dorsal inclusive. Most of the constrictor nerves pass out from the fifth to the ninth dorsal.

Back. The dorsal branches of the lumbar and intercostal arteries, issuing from the dorsal muscles to supply the skin of the back,2 can be seen to contract when the gray ramus of the corresponding sympathetic ganglia are stimulated.

Limbs.-The vaso-motor nerves of the limbs in the dog leave the spinal cord from the second dorsal to the third lumbar nerves. The area for the hind limb, according to Bayliss and Bradford, is less extensive than that for the fore limb, the former receiving constrictor fibres from nine roots, namely the third to the eleventh dorsal, the latter from six roots, the eleventh dorsal to third lumbar. Langley finds that the sympathetic constrictor and dilator fibres for the fore foot are connected with nerve-cells in the ganglion stellatum; while those for the hind foot are connected with nerve-cells in the sixth and seventh lumbar, and the first, and possibly the second, sacral ganglia.

Thompson and Bancroft have studied the nerves to the superficial veins of the hind limb. The latter finds that in general the arrangement of the vaso-motor nerves corresponds to that of the arterial vaso-motor nerves and the sweat fibres. The fibres to the superficial veins originate from the lower end (first to fourth lumbar nerves) of the region of the spinal cord supplying all the vaso-motor nerves for the hind limbs.

Tail. Stimulation of any part of the sympathetic from about the third lumbar ganglion downward almost completely stops the flow of blood from wounds in the tail. The vaso-motor fibres for the tail leave the cord chiefly in the third and fourth lumbar nerves. Their stimulation may cause primary dilatation followed by constriction.

Muscles. According to Gaskell, the section of the nerve belonging to

1 Bayliss and Starling: Journal of Physiology, 1894, xvii. p. 125.

'Langley: Journal of Physiology, 1894, xvii. p. 314.

3

Thompson Archiv für Physiologie, 1893, p. 104; Wertheimer: Archives de Physiologie, 1894, p. 724; Bancroft: American Journal of Physiology, 1898, i. p. 477; Bayliss and Bradford : Journal of Physiology, 1894, xvi. p. 16; Langley: Journal of Physiology, 1894, xvii. p. 307; Piotrowski: Archiv für die gesammte Physiologie, 1893, lv. p. 258.

Langley: Journal of Physiology, 1894, xvii. p. 311.

VOL. I.-14

any particular muscle or group of muscles causes a temporary increase in the amount of blood which flows from the muscle vein. The stimulation of the peripheral end of the nerve also increases the rate of flow through the muscle. The same increase is seen on stimulation of the nerve when the muscle is kept from contracting by curare, provided the drug is not used in amounts sufficient to paralyze the vaso-dilator nerves. Mechanical stimulation by crimping the peripheral end of the nerve gives also an increase. The existence of vaso

dilator nerves to muscles must therefore be conceded. The presence of vaso-constrictor fibres is shown by the diminution in outflow from the left femoral vein which followed Gaskell's stimulation of the peripheral end of the abdominal sympathetic in a thoroughly curarized dog, but the supply of constrictor fibres is comparatively small. In curarized animals reflex dilatation apparently follows the stimulation of the nerves the excitation of which would have caused the contraction of the muscles observed, had not the occurrence of actual contraction been prevented by the curare. The stimulation of the central end of nerves not capable of calling forth reflex contractions in the muscles observed -for example, the vagus-seems to cause constriction of the muscle-vessels.