830 T H E JOURNAL OF COMPARATIVE NEUROLOGY

Kuhlenbeck should be congratulated for having produced an emi- nently readable book which says what we know and what we do not know, which gives the opinions of the author where they are worth giving and which will, both for its erudition and for its honesty, for long remain a standard.

ASPECTS O F CEREBELLAR ANATOMY. Edited by JAN JANSEN and ALF BRODAL, Oslo, Johan Grundt Tanum. 1954. 423 p. Price $9.00.

This imposing volume, dedicated to Professor Schreiner for his 80th birthday, constitutes a major contribution to cerebellar anatomy.

It contains 7 chapters. The first, by J a n Jansen, deals with mor- phogenesis and morphology of the mammalian cerebellum. Almost half of the chapter is taken up by a description of the cerebellum of the fin-whale. The author finally arrives a t a subdivision which, somewhat abbreviated, is as follows (p. 75) :

(Reviewed hy GERHARDT VON BONIN.)

Lobuli I I1 I11

Anterior lobe I Lingula Vincula lingulae

I1 L. Centralis Ala L. eentralis

L. quadrangularis pars anterior V

Fissura prima Posterior lobe

L. simplex V1 Declive L. quadrang, pars posterior

Crus primum vII Folium 1 Tuber

L. Semilunaris superior L. Semilunaris inferior L. gracilis

Parafloceulus dors. VIII Pyramis L. biventer Paraflocculus ventr. I X Uvula Tonsilla Paraflocculus ace. Paraflocculus

F 1 o c c u 1 us

Fissura posterolateralis Lobulus jlocciilonodularis

X Nodulus Flocculus

I n each subdivision of the anterior lobe, and probably also of the posterior lobe, a vermal, an intermediate, and a lateral part can be discerned. Edinger 's subdivision into a palaeo- and neo-cerebellum is not tenable. Obviously, Bolk is also quitme untenable, for he failed to recognize a flocculonodular lobe.

,The second chapter, on the afferent connections of the cerebellum is by Brodal. He reviews the dorsal, the ventral, the intermediate

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spino-cerebellar tract (the last one of which is very weak), the cere- bellar afferents from the external cuneate nucleus, which go almost completely to the anterior lobe, the olivo-cerebellar connections, which go to the whole cerebellum and show a definite topological organiza- tion. There is an excursus on the spinal afferents to the inferior olive, which makes it clear that they only go to a part of the olive. To resume the main trend, the ponto-cerebellar connections are taken up next, and here again a fairly clear cut topographic organization can be discerned. Then the afferents to the pons are discussed: they come from the cortex, and arise there in all 4 lobes. There are some tecto-pontine fibers, and also some, although not too many, spino- pontine-fibers, showing that the porn, too, does not only rely on af- ferents from higher levels. Then reticulo-cerebellar connections are discussed, among whom the lateral reticular nucleus is treated a t greatest length. Then follow the afferents from the perihypoglossal nuclei, the rubro-cerebellar connections, the tecto-cerebellar, trigemino- and vestibulo-cerebellar connections, and a short remark on the lateral cervical nucleus, which is present only in some forms but apparently absent in others. Among those in which it is absent, is man. It is present in the cat, dog, sheep and whale. No reason for these differ- ences can be given. The projections from the spinal tracts show much less somatotopical organization than the shorter projections from the inferior olive, from the pons, etc. One gets the impression (not men- tioned by Brodal) that much of the somatotopical organization is simply a matter of getting there fastest and easiest, and has little to do with the function of the cerebellum. Lashley expressed similar views on several occasions (see e. g. Biological Symposia, vol. VII ,

I n the third chapter, the efferent connections are treated by J a n Jansen. It starts out with a consideration of the connections between the cerebellar cortex and the nuclei of the cerebellum, of which three, the nucleus fastigii, the interpositus and the lateralis are recognized. The last named is the homologue of the dentate nucleus of human anatomy, the interpositus is homologous to the globosus and emboli- formis. The three nuclei receive their afferents from different parts of the cerebellar cortex, the n. fastigii from the vermis, the inter- positus from the medial and the lateralis from the lateral part of the hemisphere. The anterior lobe of the cat, incidentally, does not have a true lateral part. The flocculus projects to the vestibular nucleus. Then follows a detailed account of the efferent pathways, the various components of the brachium conjunctivum, the fasciculus uncinatus, etc., which is good and clear. The efferent connections in man are given as a separate chapter towards the end.

There follows a short (pp. 249-261) chapter on the descending con- nections to the inferior olive by Walberg. On the whole it is very

p. 301-322).

832 THE JOURNAL OF COMPARATIVE NEUROLOGY

clear. But I have been unable to puzzle out figure 72. What does ((dorsal” and ((ventral” mean? Probably “cranial” and (‘caudal,” but why were these words not used? It is of special interest to find that there is a strong projection from the aqueductal gray of the midbrain to the inferior olive. That there is also a cortical, a caudate, a pallidal and a projection from the nucleus ruber, is better known. That all the projections partly, but only partly, overlap may also be of interest, although little is made of it in the book.

Then comes another short chapter by Harkmark on the rhombic lip and its derivatives in relation to the theory of neurobiotaxis. It goes from page 264 to page 280, and it is a sane and modern account of a theory that should have long since been discarded. Piatt is cited at the end. “When theories of forty or more years standing have received so little experimental substantiation, it behooves us to invoke them less and experiment more. ”

The 6th chapter, by Jansen and Brodal, is perhaps the most in- teresting of all. It has as its heading, The structural organization of the cerebellum, and it stresses less what we know, and more what we do not yet know about the cerebellum. It starts out with the floceulonodular lobe, which is mostly vestibular, but shows some in- teresting differences between flocculus and nodule. Extirpation of the former led to extension of the hind limbs and flexion of the fore- limbs, while the extirpation of the nodule led to the opposite symp- toms. I n discussing the possible role of the flocculonodular part on eye movements, it appears that the monkey and the guinea-pig be- have differently, that there is, in other words, a species difference which it may be well to bear in mind in other cases as well.

Then follows the anterior lobe. Three divisions, the vermis, the intermediate and the lateral region should be distinguished. The vermis receives almost exclusively spinal afTerents via ventral spino- cerebellar tract and the spino-olivary system as well as impulses via the dorsal spino-cerebellar tract, the external cuneate and the lateral reticular nucleus. The intermediate part does not receive impulses from the ventral spino-cerebellar tract o r the inferior olive, but does receive pontine fibers relaying impulses from the cerebral cortex. The lateral part receives only cortical impulses via the pons. The somato- topical organization is somewhat difficult to understand, since it is missing in many of the afferents to the anterior lobe. The idea is advanced that the lateral reticular nucleus which shows a compara- tively good somatotopical organization and seems to respond first of all to the spinal afferents, is the one responsible for giving the local sign. Also several pathways may transmit more than one kind of impulse. Thus the dorsal spino-cerebellar tract transmits not only proprioceptive, but also exteroceptive impulses. There is very little topological organization in the relays. Inhibition and facilitation from

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the cerebellum are so far more bewildering than clarifying. It may be wrong, according to the authors, to look for a somatotopical or- ganization in the reticular substance, it may be that the topical arrangement is situated in the afferent system. It should finally be mentioned that the nucleus fastigii has different connection in its rostra1 and its caudal part. Vestibular fibers may end only in the caudal part of the nucleus.

For the purpose of this ehapter the vermis of the posterior lobe is divided into two parts: the lobulus c2 on the one, and the pyramis and uvula on the other side. The former is the phylogenetically younger one. Lobulus c2 is mainly under the influence of the cerebral cortex via inferior olive and pons. It is that part of the cerebellum which receives audio-visual impulses. Uvula and pyramis are under the influence of the spinal cord and under that of the perihypoglossal nucleus and the medial reticular nucleus, thus indirectly also under that of the cerebral cortex. The pyramis is similar to the anterior lobe, but is more conoerned with eye movements, while lobulus c2 is mainly concerned with the reception of acoustic and visual stimuli. This segregation of visual and oculomotor mechanisms is at the moment inexplicable.

Very little is said about the lobulus simplex. In the ansiform lobule, the crus primum receives impulses from the

caudate nucleus, pallidum, nucleus ruber and periaquaeductal gray, the posterior crus from the periaquaeductal gray and the cerebral cortex. What exactly that means, we do not know yet, but it should be borne in mind that the intercrural fissure may be of greater impor- tance than commonly admitted. The middle folium seems to be related to the forelimb, the posterior folium t o the hindlimb. While not everything fits in with this idea, the general implication that the ansiform lobule is related to the extremities is accepted.

The paramedian lobule is not too well understood, it receives some spinal afferents and also afferents from the olive and the pons. The olivary fibers appear to be non-spinal, while those from the pons may well be spinal. On the other hand, there may be cortical impulses relayed, as we know from experimental work, through the pons, from the somatomotor and the sensory area of the cortex. By and large the paramedian lobule appears to be concerned with the extremities, the anterior part with the forelimb, the posterior part with the hind- limb.

The paraflocculus may have t o do with regulation of the axial musculature, or, in view of the rather plentiful supply with fibers from the periaquaeductal gray, with the regulation of autonomic functions.

834 THE JOURNAL O F COMPARATIVE NEUROLOGY

The chapter concludes with some general remarks on the afferent and efferent cerebellar systems, on the cerebellar cortex and on cere- bellar localization.

It appears to be clear that the flocculonodular lobe is concerned with the vestibular apparatus, the rest of the cerebellum is not so easily put into a certain category. That there are three longitudinal zones in the anterior lobe, seems clear, although it should again be emphasized that the cat has only the middle and the inner ones. The authors come back once more to the question of the somatotopic. or- ganization, again without solving it. Finally they refute Edinger ’s terms neo- and palaeo-cerebellum, which are apt to confuse rather than to clarify our conception of the cerebellum.

It is interesting that nowhere in this chapter issue is taken with the assumption that the cerebellum is part (and perhaps the most important part) of a servomechanism which would include the so- called extrapyramidal structures, several of which send their impulses to the inferior olive. That might have clarified quite a lot, for on that basis it might be quite unnecessary to look for a detailed somato- topic organization. The cerebellum might act on that part of the motor apparatus which happens to be most active. Whether such an idea could be entertained seriously, could easily be investigated ex- perimentally.

There follows a 7th chapter by Torgersen on the Occiput, the posterior cranial fossa and the cerebellum. It ends with some phylo- genetic mnsiderations which are interesting, although they somehow do not quite fit in with the tenor of the rest of the book.

The book is excellently printed and illustrated, it is a tribute not only to Norwegian science, but to Norwegian bookmaking as well. The English is good, as one would expect from the distinguished authors, and there are very few mistakes in the book. On page 22 i t is “et caetera,” instead of (‘et cetera,” and on page 180 the cere- bellar nuclei ‘(occupies” a central position.

The book should prove to be of interest not only to the student of the narrower field of cerebellar anatomy and physiology, but to every neurologist, from anatomist to clinician.

THE PYRAMIDAL TRACT, ITS STATUS IN MEDICINE. By ARTHUR M. LASSEK. Charles C Thomas, Publisher, SpringGeld, Illinois. $4.75. (Reviewed by GERHARDT VON BONIN.)

On 107 pages, a succinct account, of the pyramidal tract in man and other mammals is given. The book contains no pictures, which allows it to be printed on dull paper (60 pounds Carfac-Eggshell).