The classification into epithelial organs, connective tissues, and the more specialized muscle and nerve, was largely due to him; and he proved the presence of neuroglia in the brain and spinal cord, discovered crystalline haematoidine, and made out the structure of the umbilical cord.
The substance of the brain, spinal cord and nervetrunks is normal, but the membranes are engorged.
The activity of the spinal cord is similarly depressed.
If, for example, the brain and spinal cord removed from an animal be bruised and brought into contact with tetanus toxin, a certain amount of the toxicity disappears, as shown by injecting the mixture into another animal.
There are only two or three vertebrae which are equivalent to those of the reptiles; these true sacrals are situated in a level just behind the acetabulum; as a rule between these two primary sacral vertebrae issues the last of the spinal nerves which contributes to the composition of the sciadic plexus.
The last nerve which contributes to the ischiadic plexus leaves the spinal column in most birds either between the two primary sacral vertebrae, or just below the hindmost of them, and sends a branch to the pubic portion which is composed of post-ischiadic nerves, partly imbedded in the kidneys, and innervates the ventral muscles between the tail and pubis, together with those of the cloaca and copulatory organs.
The cobra venom is supposed to extinguish the functions of the various nerve-centres of the cerebro-spinal system, the paralysation extending from below upwards, and it has a special affinity for the respiratory centre.
- Spinal ganglion -Spinal nerve Aorta- From A.
It excites the motor areas of the spinal cord and increases their reflex irritability.
Such discharges descend the nerve fibres of the spinal cord, and through the intermediation of various spinal nerve cells excite the respiratory muscles through their motor nerves.
Thus the tonus of the motor neurons of the spinal cord is much lessened by rupture of the great afferent root cells which normally play upon them.
In large toxic and in lethal doses the activity of the spinal cord is lowered.
In man the occipital foramen, through which passes the spinal cord, is placed just behind the centre of the base of the skull, which is thus evenly balanced in the erect posture, whereas the gorilla, which goes habitually on all fours, and whose skull is inclined forward, in accordance with this posture has the foramen farther back.
Large doses also depress the nervous system, weakening the anterior horns of grey matter in the spinal cord so as ultimately to cause complete paralysis, and also causing a partial insensibility of the cutaneous nerves of touch and pain.
By similar methods nature, unassisted, betrays herself but too often; in many instances - probably originating primarily in the nervous tissues themselves - the course of disease is observed to follow certain paths with remarkable consistency, as for instance in diseases of particular tracts of the spinal cord.
His views as to the physiological functions of the spinal cord are also in agreement with recent research, and he anticipated many of the pre-eminent offices of the ductless glands which students of the present time are only beginning to discover.
Its especial affinity for the nervous system is indicated by the fact that, when all traces of it have disappeared elsewhere, it can still be detected with ease in the cerebro-spinal fluid.
All potassium salts if taken in large doses are cardiac depressants, they also depress the nervous system, especially the brain and spinal cord.
They are modifications of the lateral muscles and are supplied with numerous branches of the spinal nerves.
Castellani (6) found the organisms (most probably the same species) in the cerebro-spinal fluid of patients suffering from sleeping-sickness in Uganda; and it has since been conclusively proved by Sir David Bruce and D.
On the other hand, in some neurons, after severance of the axon from the rest of the cell (spinal motor cell), the whole nerve cell as well as the severed axon degenerates, and may eventually die and be removed.
Similarly, when the axons of the motor spinal cells are by severance of the nerve trunk of a muscle broken through, the muscle cells undergo "degeneration" - dwindle, become fatty, and alter almost beyond recognition.
Stretching of the muscles antagonistic to the extensors - namely, of the flexor muscles - reduces the jerk by inhibiting the extensor spinal nerve cells through the nervous impulses generated by the tense flexor muscles.
Exner first showed, many years ago, that the nerve impulse travels through the spinal ganglion at the same speed as along the other parts of the nerve trunk - that is, that it suffers no delay in transit through the perikarya of the afferent rootneurons.
Examination of the cerebellum by the method of Wallerian degeneration has shown that a large number of spinal and bulbar nerve cells send branches up into it.
If we assume that there is a material process at the basis of ideation, we may take the analogy of the concomitance between a spinal reflex movement and a skin sensation.
Could we assume that there is in the adult man reflex machinery which is of higher order than the merely spinal, which employs much more complex motor mechanisms than they, and is connected with a much wider range of sense organs; and could we assume that this reflex machinery, although usually associated in its action with memorial and volitional processes, may in certain circumstances be sundered from these latter and unattendant on them - may in fact continue in work when the higher processes are at a standstill - then we might imagine a condition resembling that of the somnambulistic and cataleptic states of hypnotism.
In small therapeutic and in small toxic doses atropine stimulates the motor apparatus of the spinal cord, just as it stimulates the centres in the medulla oblongata.
Corresponding with each pair of myotomes, and subject to the same alternation, two pairs of spinal nerves arise from the neurochord, namely, a right and left pair of compact dorsal sensory roots without ganglionic enlargement, and a right and left pair of ventral motor roots composed of loose fibres issuing separately from the neurochord and passing directly to their termination on the muscle-plates of the myotomes.
From the spinal mountain range a series of large rivers run in a south-easterly direction to the Gulf of Bothnia.
The alpine treeless region occupies only the upper flanks of the spinal mountain-range above an elevation varying from 1800 ft.
Ordinarily, however, it is due to some peripheral irritation which is conducted by sensory nerves to the spinal cord and thence up to the sensory centre in the brain.
Pain may be stopped by removing the cause of irritation, as, for example, by the extraction of a carious tooth or by rendering the nerveendings insensitive to irritation, as by the application of cocaine; by preventing its transmission along the spinal cord by antipyrin, phenacetin, acetanilide, cocaine, &c.; or by dulling the perceptive centre in the brain by means of opium or its alkaloids, by anaesthetics, and probably also, to a certain extent, by antipyrin and its congeners.
Intercostal neuralgia is pain affecting the nerves which emerge from the spinal cord and run along the spaces between the ribs to the front of the body.
The specially painful points are chiefly at the commencement of the nerve as it issues from the spinal canal, and at the extremities towards the front of the body, where it breaks up into filaments which ramify in the skin.
It depresses the nervous system, especially the spinal cord.
The chief difference between the action of opium and morphine is due to the presence in the former of thebaine, which readily affects the more irritable spinal cord of very young children.
At present we say of such a substance as thebaine, " it acts on the anterior cornua of grey matter in the spinal cord," but why on them and not elsewhere we do not know.
In some of the lower vertebrates quinine reduces the activity of the spinal cord, but in the human species it appears to stimulate the nervous mechanism of the uterus under certain conditions, and it is therefore included under the class of oxytocic or ecbolic drugs.
Furthermore, he indicated that the brain and spinal cord may be divided into separate parts, each part having a special function - one part ministering to motion, the other to sensation, and that the origin of the -nerves from one or other or both of those sources endows them with the peculiar property of the division whence they spring.
Lastly, he showed, both from theoretical considerations and from the result of actual experiment on the living animal, that the anterior roots of the spinal nerves are motor, while the posterior are sensory.
It seems that there is a primitive tendency in the Arthropoda for the arteries to accompany the nerve cords, and a " supra-spinal " artery - that is to say, an artery in close relation to the ventral nerve cords--has been described in several cases.
Ce, Cerebral arteries; sp, supra - spinal or medullary artery; c, caudal artery; 1, lateral anastomotic artery of Limulus.
The one fact which the Lamarckians can produce in their favour is the account of experiments by Brown-Sequard, in which he produced epilepsy in guinea-pigs by section of the large nerves or spinal cord, and in the course of which he was led to believe that in a few rare instances the artificially produced epilepsy and mutilation of the nerves was transmitted.
From 1816 he published various papers in the Edinburgh Medical and Surgical Journal, which formed the basis of his Pathological and Practical Researches on Diseases of the Brain and Spinal Cord, and of his Researches on the Diseases of the Intestinal Canal, Liver and other Viscera of the Abdomen, both published in 1828.
If a healthy spinal cord be hung up in spirit for a matter of six months or more, a glassy substance develops within it quite like true amyloid.
The remarkable physiological discoveries of Sir Charles Bell (1774-1842) and Marshall Hall (1790-1857) for the first time rendered possible the discrimination of diseases of the spinal cord.
Nor was the northern school wanting in special investigators, such as John Abercrombie (1780-1844), known for his work on diseases of the brain and spinal cord, published in 1828, and many others.
But the influence of the alkaloid upon the spinal cord is very marked and characteristic. The reflex functions of the cord are entirely abolished, and it has been experimentally shown that this is due to a direct influence upon the cells in the anterior cornua.
There appears also to be a specific action of lowering the reflex excitability of the spinal cord.
It is a muscular tonus of central source consequent on the continual glow of excitement in the spinal motor neuron, whose outgoing end plays upon the muscle cells, whose ingoing Yet when the muscular contraction is taken as index ology.
It had been held that the branches of the g3 Activity end is played upon by other neurons - spinal, cerebral and cerebellar.
Cerebro-Spinal Fever >>
Dwellings require careful construction, with thick walls and roofs of non-conducting material to keep out the heat-rays, and fans and punkahs are essential for the promotion of currents of air in the inhabited rooms. Personal protection, in the shape of thick pith topees, or cork helmets, and spinal pads, is necessary in the hot months, the clothing being light and loose and not too thin.
It is the central nervous system, and contains within itself the elements of the brain and spinal marrow of higher forms. The neurochord tapers towards its posterior end, where it is coextensive with the notochord, but ends abruptly in front, some distance behind the tip of the snout.
The first dorsal spinal nerve coincides in position with the myocomma which separates the first myotome from the second on each side, and thereafter the successive dorsal roots pass through the substance of the myocommata on their way to the skin; they are therefore septal or intersegmental in position.
These may be called the spinal eyes, and it is said that they are disposed in such a way as to receive illumination preferentially from the right side, although this fact has no relation with the side upon which Amphioxus may lie upon the sand.
In infants especially opium acts markedly upon the spinal cord, and, just as strychnine is dangerous when given to young children, so opium, because of the strychnine-like alkaloid it contains, should never be administered, under any circumstances or in any dose, to children under one year of age.
Concerning the spinal nerves and their plexus: H.
The effect of the spinal mountain range in modifying oceanic conditions is thus illustrated.
The discoveries of the separate paths of sensory and motor impulses in the spinal cord, and consequently of the laws of reflex action, by Charles Bell and Marshall Hall respectively, in their illumination of the phenomena of nervous function, may be compared with the discovery in the region of the vascular system of the circulation of the blood; for therein a key to large classes of normal and aberrant functions and a fertile principle of interpretation were obtained.
In such cases the paths of degeneration are so neatly defined that, when the tissues are prepared after death by modern methods, they are plainly to be seen running along certain columns, the subdivisions of which in the normal state may hardly be distinguishable one from another: some run in strips along the periphery of the spinal cord, at its anterior, middle or posterior segments, as the case may be; in other cases such strips occur within its substance, whether along columns of cells or of white matter.