THE LAUNCESTON GENERAL, HOSPITAL

motor nerve cells of the sympathetic Itanglla only by way of the central nervous system. Microscopicll.l examination of the, sacral spinal roots revealed to Gaskell fine. medullated fibres passing out In these roots for distribution to the bladder and large Intestine. No fihres could be found In the cervical spinal roots, but many groups of these fibres entered into the pneumogastric nerve. These fihres are widely distributed to the stomach and Intestines as far as the ileo-colic valve. Stimulation of these sacral or bulbar nerves leads to contraction of the plain muscles In the organs respectively supplied from sacral or vagal sources. The use of nicotine reveals the presence of nerve cells on the path to the periphery, the cells lying in the walls of the organ supplied by the pr-egang'ltonie nerves. There are therefore three main outflows of fine, medullated fibres to peripheral motor ganglia, the bulbar, the thoraclco-Iumbar and the sacral parts of the involuntary nervous system. These three portions are separated roughly trom each other by the nerve plexuses to the upper and lower limbs. The efferent fihres which travel trom the central nervous system Into the involuntary system are only In part motor fibres to plain muscle cells. Some of them seem concerned with the Inhibition of muscular contraction, while other fibres stimulate the secretion from glands. The motor fibres ot the thoracic region belong to the vaso-dermal system, and are distributed to the heart, to the bloodvessels of the whole body, to the musculature of the sweat glands. to all unstriped muscle found just beneath the skin of the entire body, whether the muscle Is plio-motor or not, to the plain muscle found in relation with all the structures formed from the segmental uro-genital duct, and to the sphincter muscles ot the caecum, rectum, bladder and urethra developed from the primitive cloaca. The motor fibres of the bulbar reg'ion supply the muscular layers in the wall of the alimentary canal from the ceaophagus to the end of the intestine at the lIeo-collc sphincter, while those from the sacral region supply the muscle fibres of the large intestine and bladder, excluding the sphincter muscles. The Inhibitory fibres of the thoracic region pass to the muscle fibres of the small Intestines and of part of the stomach. The muscles of these parts are supplied with a reciprocal nervous mechanism. The vagal nerve carries motor flbres which are effective through the cells of Auerbach's plexus, while the splanchnic nerves carry Inhibitory fibres which end In the superior mesenteric ganglion. Postganglionic flbres pass from the ganglion Into the gout. These fibres when stimulated have been shown by Elliott to give rise to inhibition. The flbres seem thus to be Inhibitory In the whole of their course, and to arise from "Inhibitory" nerve cells. The inhibitory fibres of the sacral region pass to the sphincter muscles of the bladder and rectum. The vagus supplies Inhibitory flbres to the heart. In all these cases a reciprocal Innervatlon Is present, derived from different regions of the central nervous system. In addition to the detailed account of the dtstrtbutton of the fibres of the rnvoluntarv inervous system to the different regions of the body, Gaskell deals with the rhythmic and peristaltic movements of involuntary muscle In a chapter In which the myogenic and neurogenic origin of the heart-beat is debated. and In which a most valuable account of the movements of the small intestines Is Included. In another chapter he discusses the pathway of the nerves which cause the secretion of duct-bearing glands. The efferent neurones for these glands lie outside the central nervous system, and belong to the Involuntary nervous system. In the case of the salivary glands, a reciprocal innervation can be recognized, but In regard to the majority of glands not sufficient Information has been collected for any useful discussion. The final chapter deals with phylogenetic origin of the sympathetic nervous system, and Is coloured by the author'a views as to the origin of the central nervous system of vertebrates from the alimentary canal of primitive T'aloeostraca, forms which were neither crustaceans or arachnids. but which gave rise to hoth groups. Gaskell also believed that the voluntary and jnvoluntary nervous svstem are hullt on the same plan. The nervous mechanism of each spinal segment consists Of an afferent neurone, which Is connected with a sensory end-organ, of a motor neurone, passing from the cord to striped muscle, and of a connecting neurone, which brings these neurones into relation with each other. to complete the refiex are. Gaskell believed that the involuntary system was arranged In the same way. The afferent fibre passed by the posterior root Into the cord, the connecting neurone was represented by the preganglionic fibre, while the motor neurone was replaced bY the fibre derived from the sympathetic ganglion. Whrle this hypothesis has the virtue of simplicity, and affords an easy method of explaining the structure of the involuntary nereous system, It does not seem to be In accord with some well-known physiological observations on the union of nerves. Langley showed that somatic spinal nerves could be joined to preganglionic fibres of the sympathetic. Thus the vagus can be joined to the cervical sympathetic trunk in the neck when it makes a functional union. Stimulation of the vagus will then dilate the pupil, constrict the blood-vessels of the ear and otherwise produce the effects of sympathetic excitation. The vagus will not make a functional union with the post-ganglionic fibres from the superior cervical ganglion passing either to the blood-vessels of the ear or to the pupil of the eye. Pre-ganglionic and not postganglionic fibres seem thus to be homologous with somatic efferent fibres. The coloured diagrams with which the book Is illustrated will repay careful study. Some of them are original, and convey their information with much ease. The work will remain a summary of the views of one who had a profound intluence on our conceptions of the physiology of man. It will be read with profit by all who take any interest in the progress of knowledge on the function of the human body. • naval and military.