made (161-168) as to the action of the nerves on the muscles and blood-vessels, are equally applicable to these flat muscles and muscular membranes.

172. The glands are a tissue of vessels and nerves, and their function is to separate the secretions from the blood. The nerves exercise the same influence on these as on other vessels, and, consequently, secretion, which ordinarily appears to be simply physical, is not only animal, but is also sometimes a sentient action. The nerves have the most manifest influence on those glands which are surrounded by muscular tissue, or so placed between muscles that the latter, by their action, express the fluid from the glands when secreted; so that it is poured out. Examples of this kind are the penis [Geilen], the urinary bladder, the bowels, the stomach; also the parotid glands, which are emptied by the action of the muscles of mastication (Haller's Physiology,' § 233.) Many glands pour out their secretions from external sensations (titillation-pain, 80); many from imaginations, sensational anticipations, desires, &c., as, for example, the salivary glands from the recollection or expectation of an agreeable taste, or in hunger; many from passions, as the lachrymal and sexual glands; many even from acts of will, as when the saliva is stimulated to flow by voluntary mastication, or weeping is feigned.

173. The action of the nerves in the viscera is very complex, varying with the number of the nerves distributed, or with the various impressions of which the latter are susceptible (34, 47, 121); or, as they are influenced by the muscles, muscular tissues, glands, &c., which surround, or are in relation to them; or, as the nerves act directly or by sympathy (127, 165). We can only notice some of the most important.

174. The stomach has many and considerable nerves, and remarkable sensibility. When the trunk of these nerves (the eighth pair) is tied, the powers of digestion fail. Its nerves are susceptible of special external impressions, so that acrid substances which are not distinguishable by the tongue excite the stomach. On the contrary, other things which the tongue perceives most sensibly, cause not only no distinct sensation, but no sensation at all, although it is manifest from the movements which they sometimes excite, that they must cause another external impression, which is not felt, because, probably,

there are natural obstacles that prevent the transmission of the impression to the brain (47); of these we shall treat in the second part (428, 429). In virtue of its sensibility, the stomach is susceptible of impressions from conceptions in the brain (98), which are sentient actions, as, for example, a violent pain causes spasms of the stomach. The observations made with reference to the action of the sensational conceptions and desires on the œsophagus and intestinal canal, are equally applicable to the stomach (170); they induce sentient actions, as, for example, when by an imagination or anticipation of a loathing, its action is inverted, and vomiting is excited; or, when it is excited to motion by hunger; or is thrown into spasmodic action by violent emotions. The will has little influence over it; but the connection between disorders of the mind and the nervous system, and disorder of the digestive powers of the stomach and bowels, is well known.

175. Although the sensibility of the liver is not great, and, consequently, only few external impressions made on its nerves reach the brain, still it is capable of sentient actions. They are observable only in the most vivid external sensations and sensational conceptions, as, for example, in the pain of inflammation, or in rage, fury, &c., inasmuch as it can be inferred from the bilious disorders which follow, as icterus, &c., that the secretion of bile must be prevented or increased. The nerves can also exercise an indirect influence on the liver through the diaphragm, and the abdominal muscles, and the other organs in relation with it, and the results are also sentient actions.

176. The kidneys have but few nerves, and are only affected by powerful external impressions and sensations, as when there is a stone or inflammation present; in which cases only, certain sentient actions occur, as spasms. The external impressions made by the urine, and which excite vivid external sensations in the nerves of the tongue, the nose, and even the skin itself, are either not made at all on the renal nerves, or a natural obstacle (17, &c.) prevents their transmission to the brain. The urinary bladder, on the other hand, is much more sensitive. Vivid external sensations (pain) cause spasms and spasmodic discharge of urine, which are sentient actions. The sensational conceptions and foreseeings act upon it, whence persons are often induced to pass urine in dreams. The will has also some influence upon it through the sphincters.

177. The organs of the external senses, considered as mechanical machines only (155) are subject to the same laws as others. Through external sensations, sensational conceptions, instincts, emotions, and even through the will, the nerves cause movement in the tongue, the nose, the ears, the eyes-even the skin in which are placed the nerves of touch, is contracted by many external sensations (as cold); all which movements are true sentient actions.

178. The sexual organs of man, and especially the testes and penis, are supplied with numerous and large nerves, which are extremely sensitive. The sensibility of the testes is so great, that syncope and convulsions are induced by injuries to them, and locked jaw, in particular, from the sympathy of their sentient actions. The sensitive nerves of the penis, which every impression excites, afford a remarkable example of the action of conceptional impressions on the vessels through the nervous loops around them, and independently of muscular action, of which mention has been already made (160), for the tumefaction of the corpora spongiosa must be caused by a retention of the blood in the vessels; which can only be explained by the theory that the nerves induce the vessels to contract. in fact, this tumefaction is excited by every kind of external impression on these nerves, especially by external sensations, as when urine irritates the bladder; semen the seminal ducts; the venereal poison, and spanish flies the urethra,—which is very sensitive; and other causes, as flogging, and friction of the glans penis. In like manner, it is caused by imaginations, foreseeings, sensational desires, instincts, and emotions, as is well known, and altogether independently of the will. Haller maintains the doctrine, that this swelling takes place without the assistance of the muscles, and solely by the blood-vessels, finding analogous instances in the erection of the nipples in sucking, the distension of the wattle of the turkey, and of the organs of generation in lower animals (Physiology,' § 810), all which are sentient actions. (Compare § 274.)

179. The numerous nerves distributed to the female organs of generation, render them extremely sensitive, and the remarks in the preceding section are equally applicable to them (274).

180. It is the most important mechanical machines of animal

bodies, that are susceptible of the sentient actions just described, in virtue of their nerves. We will now consider, in what mechanical machines, and by what laws, the different conceptive forces of the soul manifest their actions externally to the brain, in animal bodies, and in what these consist. We will begin with the sensational perception and desires (76, 89), and afterwards consider those of the intellect.

The Actions of External Sensations through the Nerves in the Mechanical Machines.

181. It is not so easy a task as it appears, to discover the direct sentient actions of external sensations in the mechanical machines. All those produced by an irritation of a nerve, or by the external impression transmitted along the nerve, or even by its propagation to the brain, or deflection thence, are its animal actions; but none is a sentient action of an external sensation (98), unless it belong to the class caused in the mechanical machines by an external sensation, or by the material cerebral sensation acting as an impression in the brain (121, 97). All movements, consequently, in the mechanical machines, which the external impression excites by its own proper animal forces, before it has formed external sensations in the brain, and all that it produces in other nerves and mechanical machines in its course to the brain, in virtue of the motive force peculiar to itself, cannot be considered as the sentient actions. of external sensations, even although they be also developed by the external sensations of the external impressions. All the sentient actions produced in the mechanical machines through the nerves only, of imaginations, foreseeings, sensational instincts, emotions, intellectual conceptions, or desires and aversions of the will, excited in the mind by external sensations, are not true direct sentient actions of the external sensations, although all the material ideas of the conceptions produced by the latter are their indirect sentient actions (97, 98).

182. Hitherto, these actions (altogether distinct) have been indiscriminately considered as direct sentient actions of external sensations, and so the physiological doctrines of external sensations have been sadly confused. It is, consequently, of im

portance, that we make this distinction as clear as possible; and to this end, we must assume,-what will be demonstrated in another part of this book for the first time, namely,— that the external impressions on the nerves (nerve-feeling, § 32), becomes itself an animal motive force, before it reaches the brain, and develops external sensations therein. The most certain answer to the question, whether a movement, excited in a mechanical machine by the external irritation of a nerve, be simply an action of the external impression (feeling), or whether it result from an external sensation, is found in the experiment of repeating the irritation, of which the movement is the result, after the nerve is cut off from connection with the brain; or, for greater security against sympathetic action, after the head of the animal has been separated entirely from the body. So long as traces of animal life remain after this separation, the same movement results from irritation of the nerve, although the external impression is no longer propagated to the brain, and no longer able to excite a material sensation therein; consequently, the movement cannot be a sentient action caused by the external sensation, but is an animal action produced by the motive force peculiar to the external impression. When after this demonstration, the apparently sentient actions of external sensations in the animal machines are investigated, it is found, that the animal motive force of unfelt external impressions can produce, although somewhat less perfectly, the greater number of these movements, which we consider as being solely sentient actions resulting from external sensations, and which are in fact sentient actions also, as will be shown in the second division of the work.

183. The movements developed in organisms by the peculiar animal moving force of the nervous system, not being at the same time an animal-sentient force (6), are termed nerve-actions, to distinguish them from sentient actions; consequently, the movements excited in organisms by the motive force of an unfelt external impression, are nerve-actions. The majority of the sentient actions in mechanical machines of external sensations are, therefore, at the same time, nerveactions (182); and the following propositions must be rejected as erroneous. 1, That an animal movement in the mechanical machines, which is a sentient action of external sensations, is