Lussana's Fisiologia dei Centri Nervosi Encefalici

Lussana's Fisiologia dei Centri Nervosi Encefalici

F. Lussana e A. Lemoigne: Fisiologia dei Centri Nervosi Encefalici. 2 vols. Padua, 1871.

The immense activity in all the schools of Europe which has, since Gall, been directed to the study of the functions of the brain, has produced but very meagre results. This is no doubt greatly due to the extreme complexity of the cerebral mechanism and the delicacy of its elements--two conditions which greatly interfere with experimental research; but it is also due to an imperfect conception of the principles which should guide such research. To suppose that organs which normally respond to stimuli so delicate and variable as the waves of molecular movement excited in a semifluid nerve, will reveal their normal functions when lacerated, pricked, galvanised, &c.--or to suppose that slicing away portions of the brain will yield more than negative evidence, and that needing very rigorous control, is to obstruct research with facts which obscure our vision, instead of illuminating it. Amid the mass of experimental evidence with which cerebral physiological literature is crowded there is extremely little which has any value; and yet it is only by experiment, rightly conducted and interpreted, that we can hope to complete and control the subjective analysis of Psychology. Physiologists and psychologists must converge their efforts. This is daily becoming more recognized. Meanwhile there is this drawback: physiologists are too much under the influence of traditional dogmas respecting Intelligence, Sensation, Volition, &c., and psychologists lend too willing an ear to the statements of physiologists, accepting with too easy a faith the premature conclusions of unverified research. Instead of meriting the old reproach of neglecting the physical basis of mind, the psychologists of to-day, for the most part, seem to me only too credulous of what physiologists tell them respecting that basis; and the successors of men who explained mental phenomena in supreme disregard of the nervous system, are now localising these phenomena in cells and convolutions, in supreme disregard of all the rest of the organism.(9 § 2 ¶ 1)

We are still a long way off a satisfactory theory of the brain; we have not even mastered its anatomy. Meanwhile every work is welcome which brings any positive evidence or suggestion; and such a work is the one which I wish to introduce to the readers of Mind. Head the scientific journals been sufficiently alert, I might have been spared the trouble; but although this work has been four years before the world, and although it was crowned by the Belgian Academy, and therefore carries its credentials with it, the mere fact of its being written in Italian seems to have excluded it from notice. I do not remember to have seen it once mentioned in any English, French, or German periodical.(9 § 2 ¶ 2)

The first volume is devoted to the cerebrum and mesencephalon. The authors begin by calling attention to the very different results which are observed during what they call the first and second experimental periods: the first comprising that variable period of hours,days, and even weeks, during which the animal has not recovered from the perturbations produced by the operation; the second, which they justly regard as the only significant period, is that in which the mutilated organism has once more returned to something like its normal activity. Neglect of this distinction causes many contradictory facts to be brought into the discussion. Making no allowance for the shock of the operation, for the anæmia, local congestions, and turbulent sensations, which follow removal of the cerebrum, experimenters attribute all the phenomena they observe to the simple absence of cerebral agency. Hence the general agreement among physiologists that the cerebrum is the organ of sensation and volition; and that its removal is followed by a somnolent stupidity and absence of spontaneity. It is thus followed. But only during the period of perturbation. Birds, reptiles, and fishes which survive this period and enter on the second period, show that after removal of the cerebrum there are still sensations, instincts, volitions and spontaneous movements having precisely the same character as those of unmutilated animals. The experiments of our authors, and their criticism of the current interpretations, are well worthy attentive consideration. They first expose in detail what are the observed facts consequent on particular operations; and having thus laid an experimental foundation, they attempt to draw conclusions from it. They show what are the effects of removing the hemispheres, first on the intelligence, then on the sensations, then on the movements and volition.(9 § 2 ¶ 3)

They next pass to the effects of unilateral removal on unilateral perception: as, for example, the blindness of the left eye after removal of the right hemisphere. Removal of both hemispheres does not destroy the sensations of sight--as they and others have proved; but although the animal can see, and avoid objects, after loss of both hemispheres, it cannot perceive the objects; and the blindness of the left eye is therefore shown to be a blindness of perception.(9 § 2 ¶ 4)

A brief, and not very trustworthy chapter on the histology and development of the brain succeeds. To this is added a good account of the olfactory lobes; and a survey of the structure of the brain in fishes, reptiles, birds, mammals, and man. In the general considerations with which the authors sum up their exposition of the cerebral functions, they adopt what may be called a phrenological stand-point, though they speak with contempt of phrenologists. Instead of lumping together all instincts under one indivisible intelligence, they insist on distinguishing the concretes expressed in these abstractions, and endeavour to localise by experiment the organs operative in each. Whereas Flourens, on the faith of his experiments, maintained that when one sensation, one instinct, one volition, one intelligent act vanished, all vanished, and when one re-appeared, all re-appeared, our authors abundantly show that some sensations and some instincts, nay some intelligent acts, disappear while others remain.(9 § 2 ¶ 5)

The relations of the optic thalami to motion and vision are then examined; and to this succeeds a chapter on the corpora quadrigemina. A survey of the mesencephalon throughout the vertebrate division concludes the first volume. The second is devoted to the peduncular system (which the researches of Meynert have lately brought into prominence), and the cerebellum; concluding with a critical examination of the chief theories propounded in explanation of the cerebellar functions. The mass of experimental evidence here adduced will some day be of great service to physiologists; but at present we are still without the guiding conception which can enable us to interpret the evidence. All that we can learn meanwhile is the kind of disturbance produced in the mechanism when certain parts of it are injured or removed. In this way the observations of our authors are significant in the case of the dove which they kept alive three years and a-half after complete removal of the cerebellum; in this bird all the normal instincts were observed except the sexual, and all the normal activities except that of muscular co-ordination of the limbs and trunk.(9 § 2 ¶ 6)

It being simply my purpose to call attention to this work, I abstain from all criticism of its statements and opinions, which could only be ventured on profitably in a more elaborate notice. One remark is all that I will add, namely, that negative evidence is not to be confounded with positive evidence: in other words, that the observation of some function being perturbed or destroyed after the injury or destruction of a part of the brain, is no more evidence that this part is the organ of the lost function, than the disturbance or cessation of a complex mechanism when a pin or wheel is removed, proves the pin or wheel to be the mechanical agent. But on the other hand, the continuance or re-appearance of a function after the destruction of a part, is positive evidence that the part in question is not the organ of this function.(9 § 2 ¶ 7)

G. H. Lewes