The Morphological Position of the Chorda Tympani in Reptiles. It is generally agreed that the Eustachean tube and tympanic cavity of the higher vertebrates are morphological derivatives of the spiracular cleft of the lower fishes. If the chorda tympani of human anatomy runs down cephalad of the tympanic cavity, as commonly taught, then the precursor of this nerve in the fishes, if such there be, should be pre-spiracular. ALLIS 1 has lately called in question the prespiracular (pre-tympanic) character of the mammalian chorda and of course the homologous nerve cannot be sought in the fishes until this point is determined. Since the mammalian chorda pursues an exceedingly tortuous course and one difficult of interpretation, it is worth while to notice the conditions in the reptiles. VERSLUYS in his recent extensive paper 2 describes and figures these relations in several types of Lacertilia and Rhynchocephalia and comes to this general conclusion: "Die chorda tympani geht vom Facialis meist an der Stelle ab, wo dieser sich mit dem eben beschriebenen sympathischen Nerven verbindet, das ist caudal von der Columella und an der inneren dorsalen Ecke des Körpers des Quadratums. Sie reicht dann längs der dorsalen und vorden Baukenhöhlenwand auf der medialen Fläche des in die Paukenhöhle vorspringenden Quadratkörpers bis zum Unterkiefer." The detailed descriptions and figures make it very plain that the chorda tympani of reptiles is pre-tympanic and therefore morphologically pre-spiracular; and in the absence of very definite proof to the contrary, we must assume the same condition to prevail among the mammals also. Mendel and Jacobsohn's Jahresbericht; Fifth Issue.' C. J. H. The issue of this Annual for 1901 reaches us early in 1903 and, like its predecessors, is an indispensable aid to all research workers in all departments of neurology and psychiatry. The plan of the work is the same as in previous issues. 1 ALLIS, E. P. The Lateral Sensory Canals, the Eye-muscles and the peripheral Distribution of certain of the Cranial Nerves of Mustelus laevis. Quart. Journ. Micro. Sci., XLV. 2, 1901. ' VERSLUYS, J. Die mittlere und äussere Ohrsphäre der Lacertilia und Rhynchocephalia. Zool. Jahr., Abt. f. Anat., XII, 1899. 3 Jahresbericht über die Leistungen und Fortschritte auf dem Gebiete der Neurologie and Psychiatrie. V. Jahrgang. Bericht über das Jahr 1901. Berlin, S. Karger, 1902. Nervous System of Myxine.1 Dr. Holm used a variety of staining methods upon strictly fresh material and is therefore in a position to add many details of importance to our knowledge of this critical form. His most serviceable preparations are those stained by the method of GOLGI and by the iron-haematoxyglin of HAIDENHAIN. The histology of the entire brain is considered; but the results, it must be confessed, are disappointing. While the paper contains much of value and is carefully wrought out and clearly arranged, yet the author has apparently failed to make the most of his material. The discussion of the medulla oblongata, comprising about half of the paper, is especially weak, due largely, it would seem, to the neglect of important recent literature, especially that coming from England and America. C. J. H. Taste and the Fifth Nerve.' The study of five consecutive cases of total removal of the Gasserian ganglion by Krause's operation shows that several weeks after the operation there is a total loss of taste on both the tip and the back of the tongue on the operated side. The author concludes that all the fibers of taste reach the brain by the root of the fifth nerve and that none of these fibers reach the brain by either the seventh or the ninth roots. The Phylogeny of the Pallium.' C. J. H. This volume, for which we are indebted to the kindness of Professor G. Elliot Smith, contains descriptions of the nervous system of the Invertebrata and of the brain and spinal cord of the Vertebrata of the collections of the Royal College of Surgeons. The Invertebrata, spinal cords of Vertebrata and brains of Fishes, Amphibia and Birds are described by Mr. R. H. Burne; the brains of the Reptilia and Mammalia by Professor G. Elliot Smith, assisted in the Primates by Mr. W. L. H. Duckworth. 1 HOLM, JOHN F. The Finer Anatomy of the Nervous System of Myxine glutinosa. Gegenbaur's Morph. Jahrb., XXIX, 3, 1901, pp. 365-401. 'Gowers, W. R. Taste and the Fifth Nerve. Journ. of Physiol. XXVIII, 4, July, 1902. Descriptive and Illustrated Catalogue of the Physiological Series of Comparative Anatomy contained in the Museum of the Royal College of Surgeons of England. Second Edition. Vol. II. London: Taylor and Francis, 1902, pp. x, 518. The volume, we should say, is very nearly an ideally perfect catalogue. With its lucid descriptions and exceptionally clear wood cuts it is of great value as a work of reference even to those who do not have access to the specimens which it describes. At the end of the descriptions of the brains is a summary which we venture to quote in full. The human brain is by no means the largest known to us. The Elephant and the Great Whales possess much larger organs, and even the extinct Sirenian Rhytina was provided with a brain of larger absolute dimensions than that of Man. In the case of these huge animals the enormous mass of the brain is probably to be explained by the fact that the increase in size of the surface of the body necessitates a corresponding growth of the neopallium (to which the great proportions are chiefly due), which is the ultimate receptive-organ for sensory impressions. In the case of the human brain, however, the Anthropoid Apes (which approach near to Man in bodily dimensions) afford us a criterion as to the amount of neopallium which may be regarded as "necessary" (in the Family Simiida) for the reception of impressions coming from such an extent of sensory surface as Man possesses. When it is remembered that the largest Ape's brain is approximately half the size of the smallest normal human brain, and the average Gorilla's brain only about one third (approximately) the weight of the average European's brain, it will then be understood how great an area of neopallium (to which the disproportionate size of the human and Anthropoid brains is chiefly due) Man possesses over and above the needs of the average member of the Simiidæ, to serve as the physical basis (so to speak) of an associative memory of immeasurably greater potentialities (for storing and comparing sensory impressions) than that of any other animal. The feature, therefore, which distinguishes the human from all other brains is the relatively enormous size of the neopallium in comparison with the minimum which the forces of natural selection have made a condition of survival in a member of the Simiidæ. ' The neopallium assumes important functions and becomes a condition of survival for the first time in the Mammalia, and in each successive epoch it has become incumbent upon every mammal either, on the one hand, to adopt some eminently safe mode of life or some special protective apparatus to avoid extinction, or, on the other hand, to "cultivate" a larger neopallium, which, as the organ of associative memory, would enable it to acquire the cunning and skill to evade danger and yet adequately attend to its needs. In many of the Eocene Mammalia (cf. the cranial cast of Dinoceras) the neopallium is reduced 1 I use the term "neopallium" (Journ. Anat. and Phys. vol. xxxv, 1901, p. 431) because the other parts of the pallium, i. e. the hippocampus and pyriform lobe, do not share in this increase. [The significance of the term "neopallium" is explained in the article here cited. Cf. also the abstract in this JOURNAL, vol. XII, p. xii.—C. J. H.] The to such diminutive proportions that the brain resembles the reptilian type; and in each successive generation the neopallium becomes larger or the creature, in self-defence, is compelled to adopt some safe form of life. The Hippopotamus and the Sirenia are examples of mammals which have not kept pace in the fierce race for neopallial supremacy but survive by adopting habits of life which are eminently safe. condition of the human brain represents the other extreme. Here the neopallium has attained its maximum development, and its possessor has not had to seek refuge either in a retired mode of life or by any protective specialisations of structure either for offence or defence, but has attained the dominant position in the animal kingdom, whilst retaining much of the generalised structural features of a primitive mammal. This expansion of the neopallium is general and not restricted to any localised areas. Thus we cannot say that the greatness of the human neopallium is to be wholly attributed to a growth of the frontal or of the parietal or of the occipital areas, as various writers have maintained; because all parts exhibit distinct evidences of extension. But some regions exhibit the effects of this general expansion more decisively than others, and many writers have assumed (quite erroneously, I believe) that such effects are to be attributed to localised growth. Thus there are very noteworthy evidences of growth in the region around the insula in the human brain, but this is probably for the most part an expression of the general extension in a region which lends itself to a clear demonstration of any increase. In the early mammals the olfactory areas form by far the greater part of the cerebral hemisphere, which is not surprising when it is recalled that the forebrain is in the primitive brain essentially an appendage, so to speak, of the smell-apparatus. When the cerebral hemisphere comes to occupy such a dominant position in the brain it is perhaps not unnatural to find that the sense of smell is the most influential and the chief source of information to the animal; or perhaps it would be more accurate to say that the olfactory sense, which conveys general information to the animal such as no other sense can bring concerning its prey (whether near or far, hidden or exposed), is much the most serviceable of all the avenues of information to the lowly mammal leading a terrestial life and therefore becomes predominant; and its particular domain-the forebrain-becomes the ruling portion of the nervous system. This early predominance of the sense of smell persists in most mammals (unless an aquatic mode of life interferes and deposes it: compare the Cetacea, Sirenia, and Pinnipedia for example) even though a large neopallium develops to receive visual, auditory, tactile, and other impressions pouring into the forebrain. In the Anthropoidea alone of non-aquatic mammals the olfactory regions undergo an absolute 1 There is no doubt that localised hypertrophies do occur, but the fundamental distinction of the human brain is the general expansion of the whole neopallium. (and not only relative, as in the Carnivora and Ungulata) dwindling, which is equally shared by the human brain, in common with those of the other Simiidæ, the Cercopithecida, and the Cebidae. But all the parts of the rhinencephalon, which are so distinct in macrosmatic mammals, can also be recognised in the human brain. The small ellipsoidal olfactory bulb is moored, so to speak, on the cribriform plate of the ethmoid bone by the olfactory nerves so that, as the place of attachment of the olfactory peduncle to the expanding cerebral hemisphere becomes removed (as a result of the forward extension of the hemisphere) progressively farther and farther backward, the peduncle becomes greatly stretched and elongated. And as this stretching involves the grey matter without lessening the number of nerve-fibers in the olfactory tract, the peduncle becomes practically what it is usually called, i. e. the olfactory "tract." The tuberculum olfactorium becomes greatly reduced and at the same time flattened, so that it is not easy to draw a line of demarcation between it and the anterior perforated space. The anterior rhinal fissure, which is present in the early human foetus vanishes (almost, if not altogether) in the adult. Part of the posterior rhinal fissure is always present in the "incisura temporalis," and sometimes (D. 710), especially in some of the non-European races, the whole of the posterior rhinal fissure is retained in that typical form which we find in the Anthropoid Apes. When this occurs we can easily recognise the caudal limits of the pyriform lobe, which otherwise becomes confused with the neopallium. The hippocampal fissure is of a peculiarly consistent nature, and is found in all mammalian brains from Ornithorhynchus to Homo. The rhinal fissure is equally sui generis and almost as constant as the hippocampal. A few small mammals, such as Notoryctes, Chlamydophorus, Chrysochloris, and some small Chiroptera, have no rhinal fissure. Of the sulci perhaps the most constant is the calcarine, which is found in the Marsupials (both Poly- and Diprotodont), in the larger Chiroptera, Galeopithecus (but not in any true Insectivore, nor, strange to relate, Rodent, so far as I am aware), and in all the Edentates, Carnivores, Ungulates, Cetaceans, and Primates. This wide distribution of the calcarine sulcus is not generally admitted, for most writers regard the calcar avis and the calcarine sulcus as the special prerogative of the Primates or even Anthropoidea, and in the celebrated controversy of 1864 the late Professor Owen strove to prove that it was confined to the human brain. It is, however, the most primitive (it may, however, first appear at the same time as the orbital and suprasylvian sulci) and widely prevalent neopallial sulcus in the Mammalia. makes its appearance in most mammals (soon after the hippocampal and rhinal fissures have developed) as a short oblique sulcus behind the splenium of the corpus callosum (or in the corresponding situation in Marsupials), and hence it is commonly called "splenial" (Krueg) in non-Primate Orders, in which its true nature has not been properly recognised hitherto. 1 1 1 Meynert and Ziehen have called the splenial sulcus "calcarine" in some Carnivores, without indicating any valid reasons for their views. They have |