The views of Bichat were generally adopted by phy-siologists until comparatively recent times, when they were ably combated by Valentin, who endeavoured to establish the doctrine, commonly held before the time of Bichat, that the sympathetic and cerebro spinal nerves do not constitute two distinct and independent systems, but that the former is dependent upon the latter for all its pro perties, and is in this respect to be regarded as one of the cerebro-spinal nerves. The in voluntary and apparently spontaneous nature of the movements which take place in organs supplied by branches of the sympathetic, affords no argument, according to Valentin, for supposing that their action is not regu lated by the brain and spinal cord, or that the sympathetic is independent of these parts of the nervous system, inasmuch as the same character is also presented by the movements of certain.; organs which are undoubtedly supplied by cerebro-spinal nerves. This, for example, is the case with the rhythmical movements of the muscles of respiration. Again, there are organs which are supplied by nerves of cerebro-spinal origin, and which notwithstanding resemble the organs supplied by the sympathetic in the circumstance that the normal impressions which are made upon, them do not reach the sensorium. Thus, the greater part of the mucous metnbrane which lines the bronchial tubes, as well as that of the oesophagus, receives its nerves from the eighth pair ; the lacrymal glands receive fila ments from the fifth nerve ; and from the fifth and seventh nerves fibres are distributed to the salivary glands : and yet all these organs present the same relations in regard to sensi bility as the pancreas or other glands which derive their nerves from the sympathetic. The fact of certain parts being beyond the control of the will, and from which the or dinary impressions they receive are not con veyed to the sensorium, does not so much depend on any peculiarity in the nerves with which they are supplied, as upon their ana tomical constitution. Such is the case, for example, with the muscular fibres presenting the same characters as those which are found in the walls of the ducts of the various glands, as well as with those which are present in the coats of the blood and lymphatic vessels. That the impossibility of influencing these structures by any effort of volition, as well as the fact of their being removed from the sphere of sen sation, do not depend on any peculiarity in the properties of their nerves, is shown, Valen tin says, by the fact that the greater part of the nerves for the salivary glands are derived, as above stated, from the fifth and seventh cerebral nerves. The same thing also holds true, according to him, of the mammary glands, the nerves supplied to which proceed chiefly frotn the supra-clavicular and inter costal nerves. As regards the argument which is drawn in favour of the views of Bichat, from anencephalous fcetuses, Valentin re marks that there is no evidence to show that in the development of the various organs in the foetus nervousinfluence is at all concerned; and, moreover, that the phenomena of growth and nutrition are not dependent on the sym pathetic is shown by the circumstance of few or no sy mpathetic fibres being sent to the extre mities. The sympathetic is moreover capable of transmitting stimuli to and from the cerebro spinal centres, in the same manner as the ordi nary nerves arising from these, though in a less degree; sthnul us applied to the spinal cord being capable of exciting contractions in the heart and intestinal canal, while on the other hand stimuli applied to the latter may also be trans mitted to the former. This is shown by the severe pain which is felt in organs supplied by the sympathetic, when affected with disease, as well as by, the circumstance that irritations of the intestinal canal not unfrequently give rise to contractions in the muscles of animal life : as is not unfrequently the case with children, when the presence of worms in the intestinal canal gives rise to impressions which are conveyed along the centripetal nerves to the spinal cord, and are there trans ferred to the motor nerves which pass to the voluntary muscles, exciting them to contrac tions. As already stated, Valentin believes that all the true nerve-fibres which are pre sent in the sympathetic, are derived from the brain and spinal cord ; on entering the syrn pathetic they pass through a greater or smaller number of its ganglia, and are then distributed to the different organs, in the same way as the ordinary cerehro-spinal nerves. The sympathetic is therefore, according to him, a cerebro-spinal nerve, possessed of the same properties, and deriving these from the same source as the other cerebro-spinal nerves ; the only peculiarities in the sympathetic being its nutnerous points of origin, as well as the large number of ganglia which it presents. Similar views are also held by Longet*, and others.
After the discovery of the gelatinous fibres in the sympathetic, it was held by some, that while motion and sensibility in the organs sup plied by this nerve depended upon the tubu lar nerve fibres sent to them through the medium of the branches of the sympathetic by the brain and spinal cord, the processes of nutrition depend upon the gelatinous or pro per sympathetic fibres. Moreover, as these fibres are found in the cerebro-spinal nerves also, it is supposed that they pass to the ex tremities along with the cerebro-spinal nerves, where they in like manner preside over the nutrition of these parts. According to these authors, the ganglia are so many centres, from which nerve fibres, possessing peculiar pro perties, pass off in different directions ; some to the viscera, others to the extremities, along with the cerebro-spinal nerves, and by means of which the nutritive processes are regulated. Thus, while the internal viscera receive sen sory and motor nerve fibres from the brain and spinal cord, they, as well as the organs of animal life, receive the nerve fibres which regulate the nutritive processes from the sym pathetic. Such seems to be the view of Remak R. Hall 1, and others.
Volkmann§ adopts the same view as was held by Bichat, regarding the sympathetic as constituting a system of nerves distinct from and independent of the cerebro-spinal system. Under the term sympathetic, he includes not only the sympathetic, commonly so called, but also the ganglia which occur on the pos terior roots of the spinal nerves, as well as those which are present on several of the cerebral nerves. All the finer nerve fibres are regarded by him as sympathetic fibres. These originate in the different ganglia ; some of them pass inwards to the viscera, over whose movements and nutrition they preside, while others pass along with the cerebro spinal nerves to the extremities, and serve as the nerves of nutrition to these parts. Each of the ganglia he regards as a nervous centre.
By the term centre, Volkmann seems to mean an organ which serves as a regulating appa ratus, and by which several separate anti simple acts arc combined into a single com plex organic act. The contraction of a muscle is a simple act ; in the act of respiration we have the contractions of many muscles com bined into a single complex act, their com bination being dependant on a power situated in the medulla oblongata, which part of the nervous system is therefore termed their cen tral organ. The question then in regard to
the independence of the s3mpathetic is, whe ther, in the sphere of the organic nerves, there be such combinations, and hether these have their centre in the brain and spinal cord, or in the sympathetic. The brain is the centre of all psychical acts ; it is therefore evident that the sympathetic, in so far as regards all the phenomena of sensation occurring in its sphere, must be regarded as dependent on the brain. But after the brain and spinal cord have been destroyed, does the sympathetic still remain active, and in such a state of acti% ity as implies the co-operation of a cen tral organ ? Aluscular motion implies the activity of the motor nerves, and the activity of those muscles which are supplied by the sympathetic must imply the activity of sym pathetic nerve fibres. The action of the heart, however, as well as the circulation, sometimes continues for weeks after the de struction of the central masses of the nervous system. Thus Bidder removed with great care the arches of the second cervical ver tebra, so that little blood was lost during the operation, and then completely destroyed the spinal cord. Frogs treated in this way often lived six weeks, sometimes ten, the circula tion, as seen in the web of the foot, remain ing at the same time active, and not differ ing from that in uninjured frogs. The heart beat powerfully and quickly: in a freshly killed frog, in winter, the heart pulsated thirty five times in the minute ; while in a frog, the spinal cord of which had been destroyed twenty-six days previously, the pulsations were forty per minute. When the brain and spinal cord were destroyed, the medulla ob longata being left, frogs were retained in life until the sixth day ; and when the entire cen tral organs of the nervous system were re moved, they lived until the second day; the rapidly ensuing death in the latter case being due, according to Volkmann, to the effects produced upon the respiration. Within a few weeks after the destruction of the spinal cord the muscles of animal life were found to have lost their irritability in a marked degree, and still later no contraction could be produced in them by application of chemical or me chanical stimuli ; the heart, however, in such cases still continued to pulsate eleven times in the minute, and retained its property of responding to external stimuli. The intes tinal canal, in like manner, retained its irrita bility ; application of stimuli giving rise to contractions which were sometimes of a local nature, -at other times extended for a con siderable distance on either side of the part stimulated. Digestion, in like manner, sutlers but little from destruction of the central parts of the nervous system ; healthy frogs, and others, which had been operated upon, were, after being starved for a considerable time, fed with worms, and kept in separate glasses. In the one, as well as in the other, the worms were found after twenty-four hours to be fully digested, and the stomach aud duodenum were filled with coloured mucus ; such was observed to be the case even in animals whose spinal cord had been destroyed twenty-six days previously. The secretion of urine also continues : when in animals in which the brain or spinal cord had been removed, the bladder was emptied by external pressure upon the walls of the abdomen, in a short tiine it again became filled and distended to an enormous size, unless emptied in the way just mentioned. It had been observed by Valentin and Stilling that after destruction of the spinal cord in the frog, different derangernents in the nutritive processes ensued ; there were frequently ob served dropsical swellings, especially of the limbs. On these also, sores formed, which often penetrated as far as the bones. In re ference to these results, Volkmann states that they are, as shown by Bidder, chiefly accidental. Bidder found that when the bottom of the vessels in which the frogs were kept xvas covered, not with water, but with moist grass or moss, no such degenerations ensued. The rapid death which ensues in warm-blooded animals, when operated upon in the above manner, depends, according to Volkmann, upon the difficulty of sufficiently keeping up the res?iration by artificial means, as well as upon the loss of blood and diminu tion of animal heat. The circumstance, then, that a certain number of the vital phenomena disappear suddenly and irrevocably after de struction of the spinal cord and brain, while others continue for a greater or shorter time, and this very perfectly, can only de pend, according to Volkmann, upon the cir cumstance that the brain and spinal cord is a necessary condition for the existence of the former, but not for that of the latter. If the latter depend upon certain nervous organs, and if the nerves of the vegetative organs do not require, as a fundamental condition of their activity, the presence of the brain and spinal cord, the only possible centres on which they can depend for this are the ganglia of the sympathetic. The synipathetic and its ganglia, then, constitute, according to Volk niann, an independent whole, from which proceed the impulses to as well as the regula tion of those actions which continue after the brain and spinal cord have been destroyed, and which notwithstanding require the co operation of a central organ. That the move ments in question require such an organ, and are not produced by the rnere stimulus of the blood, fteces, air, &T., in the same way as the twitchings of the muscles in a frog's leg are produced by galvanisrn, is shown, according to Volkmann, by the different characters ex hibited by the two. When stimulus acts im mediately on motor nerve fibres, contraction ensues only in that muscle or part of the muscle to which these are distributed ; when it affects the whole trunk of such a nerve, many muscles are excited to contraction ; the contraction so produced, however, is a mere quivering, quite different from the combined and plan-like movements of the muscles of respiration, &c., or those reflex movements which are produced artificially. In these, there is a certain unity and plan, in the others not ; the difference depending on the circum stance that in the one a regulating principle associates the muscular movements for the attainment of an organic object or purpose ; in the others this does not take place. When the regular and plan-like inanner in which the pulsations of a heart removed from the body take place, is compared with the tu multuous and purposeless quiverings of a diaphragm similarly circumstanced, it is hardly possible to suppose that the two kinds of movement proceed from the same principle. Irritability acted on by the stimulus of the blood, or air, might explain the mere con traction of the heart; the regular order, how ever, in which this takes place, implies the existence of a regulating principle ; and a re gulating principle implies the existence of a regulating apparatug. While the regular movements of the voluntary muscles suddenly cease when the brain and spinal cord are de stroyed, those of the organic muscles con tinue'; and hence their regulating apparatus cannot lie in the brain and spinal cord, and can only, therefore, be situated in the ganglia of the sympathetic.