belief that they exert some influence over the nutrition of the parts to which their nerves are distributed, we would ask what evidence there is that through the spinal cord and its nerves per se the consciousness can be affected by any external impression; and whether all the evidence of experiment and pathological observation does not tend to show, that it is only when the spinal cord is in connexion with certain encephalic centres that consciousness of an impression—that is, sensation, can be excited. Comparative Anatomy seems to us to furnish abundant ground for the belief that the optic ganglia are the centres of visual consciousnesss; that is, impressions made upon the recipient extremity of the optic nerves, and transmitted to its central termination in the ganglia, excite in them a certain change, in virtue of which we become cognizant of the impression, that is, we see. And there is the same kind of evidence for the belief that there exists in some part of that ganglionic tract which lies at the base of the brain in man, a centre of common sensation, through which the consciousness is informed of impressions made upon any part of the body to which sensory nerves are distributed. If such be the office of the thalami optici, as our authors seem most distinctly to imply when they say that these organs "may be viewed as the principal foci of sensibility, without which the mind could not perceive the physical change resulting from a sensitive impression," what possible basis is there for the idea that this attribute is distributed among the spinal ganglia? We find that when the spinal cord is cut off from the encephalic centres, impressions made upon its nerves have no more power of affecting the consciousness, than have impressions made upon an eye whose optic nerve has been divided. And we can scarcely suppose that our authors mean to imply that the sense of touch has a set of centres distinct from the centres of common sensation; since we find that when treating of that sense, they do not consider it to be anything else than "an exalted form of common sensation." We can only account for this hypothesis, in fact, by attributing it to that deficiency of clearness in their conception of abstract ideas and of precision in their use of abstract terms, on which we have already had to remark, and of which we could adduce other examples from the present chapter.

Thus we find them remarking (p. 308) that "there is nothing" in the results of lesion in the spinal cord by disease or injury "to denote that the spinal cord does not share, in some degree, in the function of sensation and voluntary motion; all that we are justified in inferring from them is, that the union of the encephalon with the spinal cord is necessary for voluntary motion and for sensation." To us, on the other hand, these results appear unmistakeably to prove that although the spinal cord, when in connexion with the brain, is the immediate recipient of those impressions which, when transmitted to the encephalon, impress the consciousness and thus give rise to sensations, and although it is probably the seat of that executive power by which the mandates of the will originating in the brain are brought to act on the muscles, yet that its relations to sensation and volition are (to use our authors' own language) purely physical; that is to say, the changes which it

undergoes merely serve to put the proper organs of sensation and volition into connexion with the outer world, just as when, at the stations of the electric telegraph, messages in cypher are received and re-transmitted without any cognizance of their meaning on the part of the signalizer, this being known only to the recipient at its termination. Our authors go on to cite the case of the Amphioxus as making it probable "that voluntary motion and sensation may exist where there is a well-developed spinal cord the anterior extremity of which tapers to a fine point." Now to us this seems a complete petitio principii; for what evidence is there that this animal even possesses sensation, much less voluntary motion? It is agreed on all hands that its eyes are rudimentary and cannot serve as instruments for vision, even if they can indicate the presence of light; yet no one would feel himself justified in asserting that this case proves that an animal can see without eyes. On what ground, then, is it affirmed that a vertebrate animal can possess volition without a cerebrum, or sensation without sensory ganglia? On no other, as it seems to us, than that vague presumption that every animal must possess volition and sensation, of which we have already pointed-out the fallacy. Certainly the actions of the creature itself do not justify any such conclusion; for they are of the simplest possible kind, not such as to afford the least evidence of the higher psychical endowments, and not more certainly indicative of sensation than many of those movements in ourselves which we know to be independent of it. If, then, we were to affirm that the Amphioxus furnishes us with a remarkable example of an animal of the Vertebrated type so low in grade of development that its life must be considered as altogether a reflex one like that of an anencephalous monster, we should, as it seems to us, state the case more consistently with facts than our authors have done, and with at least as much freedom from objectionable assumptions.

The Chapters on the Senses contain a large number of additions to our previous knowledge, on points of minute anatomy, derived from the original researches of our authors. As they give no clue, either in their preface or elsewhere, to their separate individuality, we can only guess from internal evidence that whilst the preceding chapters are the work of Dr. Todd, the anatomical portion at least of these is the contribution of Mr. Bowman. The account of the structure of the Skin is admirable, and only needs an addition on the comparative structure of the sensitive and vascular papillæ, as elucidated by the subsequent researches of Wagner and others, to be quite complete. Indeed if soda instead of potass had been used in the author's observations, for the purpose of rendering the papillæ transparent, be could scarcely have missed seeing the peculiar mode in which the nerves terminate in the sensitive papillæ, and he would have assured himself of their absence in the greater part of those which are penetrated by blood vessels. These last seem to us plainly destined for the nutrition of the epidermis. They are developed to an extraordinary extent wherever the epidermis is peculiarly thick, this being. usually the part in which there is the least tactile sensibility; thus

we do not know a better example of them than is found beneath the thick cuticular pad of the dog's foot, where they have quite the aspect (when injected) of the fungiform papillæ of the tongue; and we find them also greatly enlarged in the interior of corns. The peculiar vascular matrix of nails and hoofs, moreover, is obviously nothing else than a modification of the ordinary papillary structure, just as these organs are modifications of the epidermis.

Our authors were undoubtedly the first to give an accurate account of the diversified forms of the papillae of the Tongue; and succeeding observers have done scarcely anything but verify their descriptions. Our knowledge of the differences between the simple, the fungiform, and the conical papilla, was previously of the vaguest kind. By them first it was shown that the fungiform papillæ, in virtue of their very thin epithelium, and of their copious supply both of nerves and bloodvessels, are pre-eminently adapted to serve the purpose of gustation; whilst the conical or filiform papillæ, through the comparative thickness of their protective covering, and the stiffness and brush-like arrangement of their filamentary productions, are obviously intended rather to be subservient to the mechanical action of mastication. In carnivorous animals, and especially in the feline tribe, the conical papillæ become much stiffer and stronger, while the fungiform are relatively far less numerous; and it is obviously by the former that the rasping action is performed, by which the surface of bones is effectually cleansed of all adherent meat.

In describing the olfactive apparatus, our authors were the first to draw attention to the peculiar limitation of the "olfactory region," as marked by a sienna brown tint of the epithelium, and by a great increase in its thickness, accompanied by a remarkable loosening of its texture, so that its particles form a thick, soft, pulpy stratum, very different from the delicate yet very transparent film of flattened and ciliated epithelium-cells, which covers the sinuses and lower spongy bones; and also to the peculiar character of the olfactive nerve-filaments, these being not furnished with the white substance of Schwann, but being nucleated and finely granular in texture, and altogether resembling those "gelatinous" fibres, which were at that time currently regarded as peculiar to the sympathetic system, but which are now known to occur frequently in the cerebro-spinal nerves. In almost every part of the description of the Eye, we find matter which was at the time of its publication quite new; and much of it still remains unsuperseded by the subsequent researches of others. Of this last kind is the description of the peculiar lamellated structure of the cornea, and of the intervening tubular spaces. Mr. Bowman's account of the minute structure of the retina was the first in which any approach was made to a discrimination of its diverse elements; and we here find most of the essential facts which have been since more fully elucidated by the admirable researches of H. Müller. The close resemblance of the vesicles of the grey layer to the vesicular matter of the cerebral convolutions was specially pointed-out-a fact of peculiar interest when taken in connexion with the history of the development

of the eye, from which it appears that these two structures are actually continuous at an early period, the eye being budded-off, as it were, from the vesicle of the thalami optici. The structure and attachments of the ciliary muscle were also very carefully examined by him; and he advanced very strong grounds for the opinion of Porterfield, that its contraction serves to advance the lens towards the front of the eye, when adaptation of its focus to near objects is required. The recent researches of Cramer, Donders, and Helmholtz, however, confirmed by those of Dr. Allen Thomson, seem to have conclusively shown that the real method of adjustment is one which though formerly suggested, had been put aside by most physiologists as highly improbable, namely, an alteration in the figure of the lens; for they have demonstrated that the images of a luminous object, which, with proper management, can be seen to be reflected from the anterior and even from the posterior surface of the lens (as well as from the cornea), have their relative places and figures so altered by the direction of the eye from a remote to a near object, as unquestionably to indicate an alteration in the curvature of the reflecting surfaces. The account of the minute anatomy of the Ear, moreover, is not only distinguished by its completeness, but by the new facts ascertained by the author regarding the structure of the spinal lamina of the cochlea, the disposition and attachments of the cochlearis muscle, and the distribution of the cochlear nerves. And although the subsequent researches of Corti and others have brought into view some additional structures of a very remarkable aspect, the nature of these is as yet so problematical, that their existence affords no secure basis for physiological reasoning.

The remainder of the portion of the work devoted to the Nervous System and its functions offers no particular subject for remark; and we now pass on to that which treats of the Organic Functions. These are discussed in the usual order,-Digestion, Absorption, the Blood, Circulation, Respiration, Animal Heat, Voice, Secretion, the Ductless Glands, Generation, Development, and Lactation. This second part is fully equal to the first as regards its plan and execution; but on the one hand it contains far less original matter; whilst, on the other, having been brought out within a comparatively recent period, it is much more completely in harmony with the present state of our knowledge of the subjects it embraces. On both these accounts we shall have comparatively little to say respecting it; as we can neither have the pleasure of pointing out so frequently the special services rendered by the original researches of our authors; nor are we so often called upon to notice the errors or deficiencies which subsequent inquiry has made manifest.

Under the head of Digestion we first find described the anatomical characters of Mucous Membrane; and familiar as we now are with these, it would be ungrateful if we were not to remind our readers that it was in Mr. Bowman's article on that subject in the Cyclopædia of Anatomy' that they were first clearly enunciated; the existence of the "basement-membrane" intervening between the epithelium and the subjacent combination of fibrous tissue with blood

vessels, lymphatics, and nerves, and constituting with the epithelium the essential part of a mucous membrane, having been first discovered by him. The peculiar modification which this membrane presents in the Stomach, moreover, and the structure of the gastric glands, are more fully described in this work than they had previously been; and the two principal varieties of gastric glands, subsequently more minutely differentiated by Professor Kölliker, are clearly distinguished, with a surmise regarding their difference of function which is probably not far from the truth. The account of the saliva needs to be modified by the results of subsequent inquiries, which have shown that a considerable difference exists both in composition and properties between the fluids secreted by the several pairs of glands. The peculiar share which the epithelium of the villi has been shown by Professor Kölliker and others to take in the function of Absorption, and the changes which its cells undergo, seem to have escaped our authors' observation; although they would seem, from some parts of their description, to have nearly approached this discovery. In speaking of Peyer's glands, they adopt the view of their secreting function which was current up to within a recent period; it has now been fully proved, however, by the researches of Brücke and others, that they are appendages of the lacteal system of vessels.

The chapter on Absorption strikes us as less complete than we could desire. The anatomy of the Absorbent System is minutely detailed; the only addition which it requires being an account of the structure of the absorbent glands, as since elucidated by Kölliker. In the general views here and elsewhere expressed respecting the functions of the absorbent system, we fully accord. Our authors regard it in the light in which it was first viewed (we believe) by Dr. Carpenter, as an extended secreting and assimilating apparatus; drawing its materials on the one hand from the contents of the intestinal canal, and on the other from the superfluous fluids of the tissues; and pouring these into the sanguiferous system, after having subjected them to their peculiar converting action. But the absorbent action of the sanguiferous system is scarcely noticed, the sole mention of it that we can find (p. 279) being far less explicit than its unquestionable importance requires. For it is now quite clear that all alimentary matters which are reduced in the digestive process to a state of perfect solution, such as albumen, gelatine, sugar, and saline substances, are readily taken-up by the blood vessels; and that foreign matters, such as alcohol and poisons generally, are received into the system almost if not quite exclusively through this channel; the special function of the lacteals being to absorb and prepare that peculiar combination of oleaginous and albuminous matter known as chyle, which is remarkably constant in its composition, whatever be the nature of the contents of the alimentary canal, whilst the composition of the blood of the mesenteric veins is greatly influenced by what it has taken up of these. Further, it has been clearly shown by the experiments of Bernard, that the liver exercises an important assimilating influence upon certain of the matters absorbed by the gastro-intestinal blood-vessels; and of his