thought be an electric fire or a movement of the vital spirits; whether souls and bodies exercise a real or an ideal influence on each other; whether souls form their bodies, or whether they are diffused through them or dwell only in the head; whether an instinctive impulse (Trieb) or a passion belongs to the body or the soul; or whether the vital spirits be elastic or inflexible, electrical or etherial, &c.; and all this has been done without any beneficial results whatever, but rather the contrary." (Preface.)

It appears, then, that Unzer had in view a clear and definite object, and that was to rival Newton and the physical philosophers (the physiciens, as they are yet termed in France), by demonstrating the existence of a new and independent class of forces or powers inherent in living matter, and by definitely fixing the laws by which they act. To facilitate the comprehension of his views, we will designate these forces or powers as the vital, -or, if that term be too hackneyed, as the biotic-forces or powers.

Seeing how much philosophers had erred in their inquiries, on the one hand, by referring, with Stahl, all the animal forces or powers to the mental force only; or with the mathematical and mechanical, by excluding the idea of vital forces, and referring everything to the laws of matter only, our author was induced to reconsider the question, to separate the vital forces from the physical, and to analyse and arrange the former according to their manifest phenomena; in short, to consider the physiology of the proper or peculiar animal (biotic) nature of animal bodies, as distinct from the physiology of the whole animal mechanism. He acknowledges the imperfect nature of his views, but modestly expresses a hope that some other and better students of animal nature, of which our time affords so many, and with whom he is not to be put in comparison, stimulated by these researches, may draw up and produce a much more comprehensive system," he being contented with the honour of having struck out the idea; or, if he might flatter himself that some much more eminent person than himself, adopting his plan of a physiology, would bring out a pathology of proper biotic nature, he would esteem himself fortunate in having the honour of paving the way to such an improvement in the art of medicine.

Plan of the work. Unzer having explained his general views and objects, gives a sketch of the plan he proposes to adopt in developing the laws of the biotic forces or powers. Their seat or origin is in the socalled proper animal machinery or mechanism, namely, the brain and nerves, furnished with the vital or animal spirits, or nervous fluid (Lebensgeister-Nervensaft), through which they are communicated to the mechanism or machines of the body. These "machines" of the body are in fact the organs of the body as displayed by anatomists, and are divided into two kinds, according to their uses. Those are simply mechanical in which the laws of physical science are seen operating, as the bones, considered as levers; the tendons as pulleys, the arteries as tubes, &c.; while those are "animal" which are directly subservient to thought, and in which the forces of life are seen to act. The term maschinen is evidently used as correlative with the biotic forces or powers: these put in motion the "machines" just as the elastic force of vapour puts in motion the steam-engine. As, however, Unzer considers muscular fibre " a machine," the term organ is scarcely synonymous with "maschinen," we shall therefore translate it literally,-machines, thinking it better to sacrifice ele

gance to a truthful expression of the author's meaning. The animal or biotic machines are the brain and nerves, or the whole nervous system; the mechanical machines are the muscles, tendons, skin and membranes, blood-vessels, glands, viscera, &c. Many of these latter are, however, considered to be endowed with biotic forces, but only secondarily, by means of the nerves ramifying through them. This will be referred to again.

Biotic forces may act either with or without the consciousness and will of the animal-or, literally, the thinking force or power-Vorstellungskraft. Now, this is a new force, and it will be well to ascertain the precise meaning our author wishes to express by it, since it plays an important part in his physiology. Looking into the context we find it is used in two or three senses. It means soul or mind, since it is used synonymously with "Seele." It further means sensation, or consciousness of an impression, or of the changes induced thereby in the brain, so that an animal with this kind of "Seele" (unvernüftige) is a sensational animal as opposed to an animal with reason-vernuftige Seele. It is also used to signify the power of thought and will, or mind, in its highest meaning, and in this sense the Vorstellungskraft can excite or originate those material changes in the brain, which are necessary to thought and volition, as well as be conscious of them when excited by impressions only. Thus sensation, or consciousness of impressions, is not, in Unzer's views, a primary force, since it cannot act on the brain or system generally without being excited; on the other hand, the mind or soul is a primary force, inasmuch as it can originate material changes in the brain and nervous system.

There are a few other terms, whose precise signification it will be subsequently necessary to define, but the preceding is sufficient to enable us to understand the author's plan.

The First Part considers the physiology of the brain, and includes the operations of the mind, whether sensational or reasoning. In the Second Part the physiology of the spinal cord and nerves is expounded, and reflex phenomena are fully defined and analysed. In the Third Part we have the economy of the whole of the animal forces or powers considered; a definition of animated nature and an arrangement according to leading types, and especially indicating animals without consciousness; animals with sensation only; and animals with reason. And lastly, an essay on the origin, life, perfection, decline, and death of animal nature. Such is the plan of Unzer's work as laid down by himself; and, after again modestly acknowledging imperfections, inviting his readers to do better than he has done or can do, declaring his willingness to profit by fair criticism, and his determination not to notice personalities, he addresses himself to his task.

In the first chapter of the first part, he states his views of the nature of the machines subservient to the biotic and psychical powers of animals, or in other words, of the anatomy of the nervous system in man and the lower creatures; these are principally taken from Haller. The brainthe seat of mind, or "the soul"-and the nerves, are the two great portions of the nervous system, the latter all ending in the former as the great centre; the spinal cord being considered according to the current doctrines, as in some degree a bundle of nerves. With regard to the ganglia, he thinks that, like the brain, they are endowed with the property of reflecting impressions.

"It is also a settled fact that the ganglia are always larger than the nerve arising from it, and sometimes very remarkably so. It is also certain that almost all the ganglia give off more nerves than they receive, and that they also as well as the brain give origin to nervous twigs; whence it is very probable that they also, like the brain, reflect certain impressions that they have received, to the limbs they govern along the new nerves that spring from them, although the impressions do not in this case become objects of consciousness, as in the brain. But more of this afterwards." (p. 30.)

The nerves are motor and sensory, and are endowed (in common with the brain) with the vital spirits or nervous fluid, (Lebensgeister-Nervensaft) the office of which is to carry impressions to and from the brain along the nerves. It is formed from the blood-vessels in the gray matter of the brain, and may be increased or diminished, and the functions of the nervous system changed accordingly. Whatever impairs its production in the brain, or hinders its transmission along the nerves, interrupts the action of the powers or forces of the mind and the nerves. Thus congestion, or compression of the brain, or division of the nerve, will stop the operations of the vital spirits or nervous fluid. On the other hand, sleep, wine, and alcoholic stimulants, agreeable passions, pleasant mental stimuli, &c., increase the quantity of the vital spirits and correspondingly exalt the functions of the nervous system. All this, however, is stated by Unzer in deference to authority only-that of Haller. Having propounded the current opinions, he dismisses them with the remark, that little is known respecting the nature of these vital spirits, and that little is very uncertain and at the best only probable; and further, that they really are not necessary to the study of the laws of the proper animal forces. Henceforth therefore, he says no more about them. He seems glad to get rid of them, but influenced by conventional feelings, buries them in forgetfulness with ceremonial respect. In his answer to one of his reviewers, he again maintains that the theory of "vital spirits" is not necessary to his

views.

Physiology of the brain its biotic forces considered as bio-psychical forces (thierische Seelenkräfte). After observing that the alternate elevation and depression of the brain is a mere mechanical movement, and dependent on physical forces, Unzer proceeds with the proper physiology of the brain as a vital or biotic "machine." First, he observes that the brain is the seat of mind or "the soul," that is a fundamental proposition which all experience proves, conflicting statements to the contrary notwithstanding. It is also a compound organ, for certain parts being injured certain conceptions or sensations do not occur, and the ideas, desires, and instincts connected with them are prevented or disappear. The property or power which Unzer attributes to the brain in particular, is that in virtue of which those changes that are necessary to every act of thought are excited; but he shall speak for himself.

"When a thought arises in the mind, a change must necessarily occur concurrently therewith, without which the conceptive faculty (Vorstellungskraft) cannot act; and when this change occurs in the brain, the conceptive faculty is necessarily excited into action. Whatever may be reasoned on the matter, a change in the brain must consist in a movement (Bewegung), and the medullary matter must also be endowed with a power of exciting movement (Bewegendekraft), which acts in harmony with the mind (Vorstellungskraft). So that each distinct class of perceptions is always connected with a certain animal (biotic)

movement, and with these movements a certain class of perceptions, for it is ascertained from numerous observations that after certain injuries of the medullary portion of the brain, especially that part from which nerves of sensation arise, certain kinds of perceptions, as for example, certain sensations (Empfindungen) are prevented or disappear, and together with them all the ideas, desires and instincts dependent thereon, as well as other faculties of the mind. This power of the brain to excite movement (die Bewegendekraft) which is thus connected with the mind and power of thought is an animal soul force (thierische Seelenkraft), and hence arises the fundamental general principle in the doctrines of the connexion between body and mind, that the medullary matter of the brain possesses an animal soul-force (thierische Seelenkraft), by means of which at every act of mind (Vorstellung in der Seele), whether it be a sensation (Empfindung), imagination (Einbildung), desire (Begierde), reflection (Betrachtung), or influence (Einfluss), it [the brain] produces in itself a certain animal movement necessary thereto, without which the act of thought can neither arise nor continue, and with which it infallibly arises and continues. This animal soul-force is peculiar to the brain, and is the property of no other animal machines, because in none other except in the brain does an animal movement develop perceptions. The medullary matter of the brain can also with propriety be designated the only instrument of the conceptive power of the mind, by means of the animal movements of which it [the mind] puts its force into action, and continues it [in action] and without which [the animal movements of the medullary matter] it would absolutely remain inactive. Philosophers have already introduced the phrase material ideas to express those movements in the brain that are necessarily connected with each act of thought. (Baumgartner's Metaphysics, § 416.) A psychological materialist considers these material ideas as the ideas of the mind itself. But since it must be firmly maintained that the thinking faculty is an immaterial substance (Substanz), it cannot certainly be granted that these changes in the brain are really ideas; but since the two are inseparably connected with each other, and the mind never acts without these movements nor can act in animals, it is fully established that every act of thought presupposes and causes a movement in the brain (material idea), and every such movement in the brain presupposes and causes an idea in the mind (Vorstellung in der Seele.)" (pp, 41-2.)

Unzer's doctrine of "material ideas" differs in little respect, if any, from that of the most esteemed metaphysicians. All acknowledge and maintain that a change takes place in the brain with each act of thought. Reid, for example, says, "In perception the object produces some change in the organ; the organ produces some change in the nerve; and the nerve produces some change in the brain." Newton, Dr. S. Clarke, Locke, Malebranche, Hooke, Descartes, Bonnet, and others held similar doctrines. In adopting it Unzer expressly cautions his readers in a special note against a misapprehension of his meaning. He has no intention of giving the notion that there are hieroglyphical figures on the brain, or impressions literally made upon it. Unzer's "material ideas" are altogether different from Dr. Laycock's "psychical substrata." Dr. Laycock wishes to express by that term, certain changes in the molecular constitution or arrangement of the neurine induced by frequently recurring impressions communicated from without, and corresponding to those impressions and to none other. These "psychical substrata" are therefore part of the constitution of the body; consequently like other organic properties, are transmitted from parents to offspring, and constitute the foundation of characteristic or acquired instincts, propensities, &c.*

Unzer uses as synonymous with "material ideas" the term "impressions,"

Essay on the Reflex Function of the Brain.-By T. Laycock, M.D.- British and Foreign Medical Review, Vol. XIX, p. 308.

inasmuch as by the latter he wishes to signify the continuous changes which continued operations of the mind excite in the brain. He also uses, but once or twice only, the term Bilder der Vorstellungen-images of conceptions, to express the same thing. However, he expressly maintains that the strength of a perception or conception is in proportion to the activity of the movement, or in other words, to the intensity of the material idea. A large material idea comprises or is made up of smaller ones, and this constitutes a large conception (grössere Vorstellung). For the term "animal soul-force," used to designate the efficient cause of these changes, and which is peculiar to the brain (quotation, p. 186), we shall substitute the term cerebral power.

Conceptions may be of two kinds. The one are dependent on movements in the brain (material ideas), which are induced by impressions on the senses; the other are dependent on movements of the brain (material ideas), induced by the conceiving force or power of the mind. The former are termed sentient or sensational (sinnliche) conceptions, or simply natural conceptions; the latter are termed arbitrary, or spontaneous, or "physiologically free." These terms are derived from Baumgärtner, who appears to have followed Locke. Unzer specially distinguishes between these two classes of ideas or conceptions. Those of sensations are altogether dependent on impressions made on the brain; the ideas of the intellect are dependent on the immaterial essence—the soul. As no conception can occur without this change in the brain termed a material idea, Unzer proceeds to inquire how these changes are excited in the brain, and what actions they induce in the animal economy; and this leads him to the consideration of the biotic force of the brain, for that is the force which develops the material ideas, and his first chapter is on external sensual impressions.

The biotic properties of the nerves. The nerves, Unzer observes, have two points; the one is that connected with the brain, the other is the termination in the body, or on the surface. If either end be irritated, the irritation is propagated to the other extremity. If a nerve be irritated in any part of its course, irritation is propagated in both directions; and if it be cut, and the cut ends irritated, if that next the brain be touched, the irritation is propagated to the brain; if that next the periphery, the irritation goes to the periphery. When an animal apparatus (a nerve) is so influenced, either by a touch or a transmitted movement, or by any other impression of whatever kind it may be, that animal actions (Wirkungen) are excited, the change thus induced in the "machine" is termed a sentient impression (sinnliche Eindrück) or nerve-feeling (Nervengefühl). Thus, a sentient impression made on a nerve will travel from the cerebral to the peripheral extremity, and vice versa. If it be made on the peripheral extremity or on the trunk of the nerve, and goes on to the brain, Unzer distinguishes it as an external sentient impression: or as a synonym, a "nerve-feeling from without inwards." But the irritation must excite changes in the animal "machine" to become an impression. Light may be applied to the most delicate and most exposed nerves of the skin, but it excites ordinarily no external sentient impression. The excitation. of the requisite change is purely animal, and quite unconnected with the mechanical or physical laws of matter. When the medulla of the nerve is touched, and the most energetic animal actions follow, as conceptions of the mind; or movements are excited by the cerebral forces, or