The evidence would tend to show that the weakness in the two cases is due to different causes.

PART III.-Results of Absinthe Stimulation.

The absinthe has been injected either immediately after the operation or after complete recovery. There are, therefore, two categories of experiments, viz., "immediate" and "remote"; but, as a rule, the difference between the average results in both cases is slight. The fit was registered by spring myographs attached to the extensor tendons of the fore paws.

1. Removal of one Cerebral Hemisphere, or Hemisection of the Mesencephalon, and Immediate or Remote Absinthe Stimulation.

Result.-There are bilateral fits. On the paretic side the initial fit may be much smaller than on the left side; in the subsequent fits, tonus is more marked than clonus; the final clonic contractions are less numerous.

2. Removal of Left Motor Area; Immediate and Remote Stimulation.

Result. The fits upon the right and left sides more closely resemble one another; there is considerable clonus upon the "paretic " side as well as upon the normal.

3. Removal of both Hemispheres.

Result.-Immediate removal of the hemispheres arrests the fits; a slight respiratory response can, however, be elicited. Where one hemisphere has been first removed, and after recovery the remaining hemisphere and absinthe has been given, contractions have been obtained, occurring at regular intervals and equal upon both sides; in one case the contraction was most marked upon the side corresponding to the hemisphere first removed. Removal of both hemispheres and stimulation upon the second day was followed by two strong fits, made up of a series of contractions following one another fairly rapidly, but not so rapidly as in the clonus when a hemisphere is present.

Where both motor areas have been removed in succession, regular tonic and clonic bilateral responses have been obtained; the rhythm of the clonus is much slower than when the cortex is intact.

4. Removal of Cerebellum and Immediate Absinthe Stimulation. Removal of one Lobe of the Cerebellum. Removal of Left Hemisphere and Left Lobe of the Cerebellum. Removal of Left Hemisphere and Right Lobe of the Cerebellum and v. v. Immediate and Remote Absinthe Stimulation.

Result.-Removal of the whole cerebellum does not stop the fits, nor impart to them any special character. Removal of one lobe of the cerebellum appears to have very little effect upon the fits. Where, in addition the opposite cerebral hemisphere is removed, the fits appear similar to those seen when the hemisphere alone is removed.

5. Removal of Left Hemisphere and Subsequent Section of the Right and Left Halves of the Cervical Spinal Cord.

Result.-Conduction abolished on the side of section.

6. Hemisection of the Upper Cervical Spinal Cord and Absinthe Stimu lation.

Result.-In cats which have partially recovered from the effects of the hemisection, absinthe produces a response upon the side which was divided.

7. Complete Section in the Dorsal Region.

Result.-In two cases of complete recovery (complete paralysis of the hind quarters remaining), absinthe did not elicit a response from the distal segment of the cord; the experiments, however, require repeating.

PART IV.-Conclusions.

The formation of the descending system of the anterior, anterolateral, and lateral columns can be seen in the mesencephalon.

There is a marked decussation of the lateral and antero-lateral column fibres in the mesencephalon. The anterior column fibres (post.-longitudinal bundle) appear to be direct fibres Decussation is, however, not limited to this region; it occurs in the spinal cord, and probably throughout the bulbo-spinal system.

Decussation of the pyramidal system is not limited to the cervical region; it occurs in the higher segments. As in the preceding system so in this, there is a direct path-the direct lateral pyramidal tract, and there is evidence of direct fibres in the higher segments.

There is bilateral distribution of both systems of fibres, but there is no evidence whatever of recrossed fibres.

No fibres get into the opposite pyramid by way of the corpus callosum.

Stimulation with absinthe shows that the bulbo-spinal centres (including the cerebellum) alone, can produce a series of clonic fits, differing from the cortical in the much slower rhythm of the contractions. But from the complete section of the cord experiments it seems improbable that the cord alone can be excited by absinthe.

Immediate hemisection of the cord prevents the absinthe fit on that side; but after recovery a modified fit results upon the side of the lesion, in spite of the fact that the direct lateral and crossed pyramidal tracts are completely degenerate, as well as the internuncial fibres in the anterior and lateral columns.

When one hemisphere is removed or a complete hemisection made in the quadrigeminal region, there are bilateral fits, in spite of the fact that one pyramidal system is completely degenerate. The fits are modified upon the side opposite to the lesion, the clonus being less marked, and the first fit being absent or very small.

If, in the last two cases, a hemisection is made upon the side of the degenerate pyramid, it instantly arrests the fits upon that side, the section interrupting the sound direct pyramidal tract.

I therefore conclude that the maximal effect of absinthe is produced when the motor area is present, and that the impulses generated there are distributed by the pyramidal system in the way described, the maximal effect crossing to the opposite side, the question of unilaterality or bilaterality being one of degree as shown by the differences between the initial and subsequent fits, and as borne out by the relative sizes of the crossed and uncrossed tracts.

The epilepsy due to absinthe indicates that there are probably very many epileptiform attacks in man which are toxic.

VI. "A Research into the Elasticity of the Living Brain, and the Conditions governing the Recovery of the Brain after Compression for Short Periods." By A. G. Levy, M.B. (London). Communicated by Professor HORSLEY, F.R.S. Received February 21, 1894.

(From the Laboratory of the Pathological Department of University College,

London.)
(Abstract.)

(Towards the expenses of this research a grant was made by the British Medical Association at the recommendation of the Scientific Grants Committee.)

In view of the great frequency of compression of the brain as a pathological condition, it seems very advisable to attempt to obtain

some knowledge of the elementary factors conditioning the physical changes in the brain substance due to mechanical pressure.

Grashey has already definitely proved that the coefficient of compressibility of the dead brain is slightly less than that of water, which is equivalent to saying that under any ordinary pathological conditions the brain tissue is incompressible. At the suggestion of Professor V. Horsley, who devised an apparatus for the purpose, and to whom I am indebted for advice and suggestions, an attempt was made to determine the elasticity of the living brain, i.e., of the brain mass with its full complement of circulating blood and lymph, and further to test the truth of the generally accepted view that the elasticity of the brain is proportional to the blood pressure.

The brain was experimented upon in situ, the influence of the cerebro-spinal fluid being excluded by the mere fact of the skull being opened and the membranes partially reflected, thus releasing the fluid from all tension. Thus we arrive at the properties of the brain mass itself as it rests upon its osseous enclosure.

There were, in the first place, considered the results of experiments performed upon freshly-exposed brains, the blood pressure being at its normal height, in order to arrive at some conclusion as to the normal elasticity of the brain. The downward movement of a plunger was measured after a given interval of time, and the extent of this is termed the "excursion." The recovery of the brain surface, to the extent of which the term "recoil" is applied, was measured until it failed to perceptibly develop further. The general character of the excursion is that of a rapid plunge downwards taking place within the space of one or two seconds, followed by a much more gradual compression. Its extent varies within a considerable range in different animals; thus a weight of 50 grams applied for one minute produces an excursion which varies in different dogs from 4.5 to 7.3 mm. It also varies notably with the weight employed. There is no obvious relation between the depth of excursion and the blood pressure.

For convenience of expression and of comparison the ratio of the excursion to the recoil is in the full paper expressed in the form of a fraction, and this ratio is termed the "proportionate recoil;" the smaller this fraction the feebler the elastic reaction it denotes, and vice-versa. A comparison of the ratios derived from experiments performed under like conditions upon different animals brings out the striking approximation which they bear to one another, whatever the length of the excursion and whatever the existing blood pressure may be. And such deviations from the average as the ratios present cannot be found to have any relation to variations in either excursion or blood Grashey, " Ueber Hirndruck und Hirncompression." Allg. Ztechr. f. Psychiat.,' Berlin, 1887, vol. 43.

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pressure. A compression by a 50-gram weight for a period of from 30 seconds to one minute yields an average proportionate recoil of §. A further comparison definitely shows that the longer the period of compression the less is the recoil; thus with a compression of only two seconds the reaction is sometimes almost perfect, whereas a compression lasting six miuutes yields a ratio of 1/2-74. Heavier weights similarly damage the brain in a fashion prejudicial to its

recovery.

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A series of experiments were performed with a view to comparing the "elasticity" of the brain at the normal blood pressure with the elasticity "of the same brain at an artificially lowered blood pressure. The first method employed was that of producing a large fall of blood pressure by bleeding. The results tended to confirm the impression that there exists no constant relation between brain elasticity and blood pressure. This series is somewhat vitiated by the partial collapse of the cerebrum which ensues during the process of bleeding, and a second series was instituted, in which the blood pressure was lowered through the agency of amyl nitrite; the brain at the moment of administration becoming flushed with blood, it has no tendency to collapse. Under the influence of this drug the cerebral vascular conditions are such that the "elasticity" is actually increased, thus conclusively demonstrating the non-dependence of the latter upon the central arterial pressure.

A further series of experiments were performed in view of the influence which venous pressure is believed to exert upon the cerebral circulation. This object was carried out by exposing the accessible cranial veins and clamping them in succession, and by measuring the variation in the intra-cranial pressure induced by this means. The results tended to show that the increase of intra-cranial pressure must be considerable to influence the "elasticity" in even a small degree.

Experiments performed upon brains which had undergone prolonged or severe compression showed that a considerable increase of arterial blood pressure is quite unable to restore the volume of the brain thus damaged, whereas an increase of venous pressure, obtained by asphyxiation, rapidly, and usually completely, brings this about.