NERIUM. 



NERVOUS SYSTEM. 



Dr. J. E. Gray makes the Naticida the first family of his seconc 

 section, Eriophthalma (Edriopthalma ?), of his second order Phyto 

 phaga. Under the Naticidce he comprises the following genera : 

 Natica, Neverita, Nacca, Cepatia, Polinices, Mammilla, Cernina 

 Gloljulvu, Naticina, Cryptoatoma, Stylina (?), Radula (?), and Neriiopsis 

 In Woodward's ' Manual of the Mollusca ' the ffaticida include the 

 genera Natica, Sigaretui, Lamellaria, Narica, and Vclutina. 



Xinety recent species of Natica have been recorded. They are 

 inhabitants of the Arctic Seas, Great .Britain, the Mediterranean anc 

 Caspian Seas, India, Australia, China, Panama, and the West Indies 

 The fosail species amount to 260. 



Sigaretui has 26 recent and 10 fossil species. 

 Lamellaria has 5 recent and 2 fossil species. 



a has 6 recent and 4 fossil species. 

 Vetutina hag 4 recent and 3 fossil species. 

 In Forbes and Hanlej-'s 'British Mollusca' the following species ot 

 Neritida; and Xaticida are enumerated as British : Neritinajlunalilii, 

 i monilifera, N. nitida, ?f. sordida, X. Montayui, *V. lleUcoida, 

 X. i-iifilla, and X. Kinyii. 



XK1UUM (from n)p<5?, humid, the habitat of the species), a genus 

 of Plants belonging to the natural order Apocynacea. It has a hypo- 

 crateriform corolla, the orifice surmounted by lacerated multifid pro- 

 cesses ; segments of the limb contorted ; the filaments are inserted 

 into the middle of the tube ; the anthers sagittate, adhering by the 

 middle to the stigma ; it has two ovaries, a filiform style dilated at 

 the apex, and an obtuse stigma. 



N. oiioratum hag linear-lanceolate leaves, three in a whorl ; the seg- 

 ments of the calyx erect ; appendages of the corolla filamentous ; the 

 anthers bearded at the point The flowers red or white, with an 

 agreeable musky scent. The bark of the root and the sweet-smelling 

 leaves are supposed by native Indian doctors to act as powerful 

 repellants applied externally. The root, taken internally, acts as a 

 poison. 



A'. Oleander, Common Oleander, has lanceolate leaves, three in a 

 whorl being beneath, the segments of the corona trifid. It is a native 

 of the Indies, in humid places, but has now beoome wild in the south 

 of Europe, by the side of streams and the sea-coast. The flowers are 

 rather large and of a bright-red colour. This species contains a great 

 quantity of gallic acid, and a decoction of the leaves or bark forms an 

 acrid stimulating wash, much employed, by the poor people in the 

 south of France to cure cutaneous disorders. The peasants in the 

 neighbourhood of Nice u?e the powdered bark and wood of the 

 Oleander to poison rats. Several cases are also recorded of death 

 from having eaten meat roasted on a spit of Oleander wood. 



All the species of Oleander are very showy when in blossom. They 

 thrive well in a light rich soil ; and cuttings strike root freely in n 

 moist situation. All of them require a good deal of heat to flower 

 well in this country. 



(Don, IHchlamydeoul Planlt ; Lindley, Flora Medica ; Burnett, 

 Outlina of Botany.) 



NKUVOUS SVSTEM. ThU system constitutes one of the most 

 essential and characteristic parts of the animal frame. It consists of 

 two portions, the Cerebro-Spinal and the Sympathetic, or Ganglionic, 

 each of which, although possessing many things in common, is dis- 

 tinguished by many peculiarities of structure and function. 



The Cerebro-Spinal system includes the brain, spinal chord, and the 

 nerves proceeding from these organs. It is through the medium of 

 this part of the nervous system that the functions of mind, sensation, 

 and volition are performed. This part was called by Bichat the Nervous 

 System of Animal Life. The Sympathetic, or Ganglionic, portion was 

 named by Bichat the Nervous System of Organic Life. These names 

 however involve theories which are not confirmed by recent researches. 

 The sympathetic system consists essentially of a chain of ganglia con- 

 nected by nervous chords, which extends from the cranium to the 

 pelvis along each side of the vertebral column, and from which nerves 

 pass to the abdominal, thoracic, and pelvic viscera. 



When examined under the microscope the tissue of which the 

 whole nervous system is composed, may be separated into two elements, 

 the Vesicular and the Fibrous. The vesicular nervous matter is gray 

 or cineritiotis in colour and granular in its texture, containing nucleated 

 nerve-vesicles, and is largely supplied with blood. The fibrous nerv- 

 ous matter is, on the other hand, usually white, and composed of 

 tubular fibres, although in some parts it is gray, and consists of solid 

 fibres ; it is also less vascular than the preceding. The former is 

 more immediately associated with the mind, and is the originating 

 seat of the force manifested in nervous actions ; while the latter is 

 simply the propagator of impressions made on it. The union of these 

 two kinds of matter constitutes a Nervous Centre, and the threads of 

 fibrous matter which pass to or from it are called Nerves. The smaller 

 nervous centres are termed Ganglia ; the larger ones are the Brain and 

 Spinal Chord. 



The Tubular Fibre is a tube composed externally of a fine trans- 

 parent homogeneous membrane, very much resembling the sarcolemma 

 of muscle. Nucleated cells may however be occasionally seen in it, 

 is mfig. \, which represents a portion of the sciatic nerve of a frog. 

 This may be termed the tubular membrane of nerve. The contents 

 of this tube consist of a soft, semi-fluid, whitish, pulpy substance, 

 which n readily pressed out of its cut extremity. This is termed by 



Fi(f. ]. 



Schwann the white substance, Fig. 2 is a nerve, that is, a sheath 

 containing a number of nervous filaments branching and receiving 

 branches from another adjacent to it. Fig. 3 is a portion of nerve in 

 which the sheath has been removed and the fibres and smaller fasciculi 

 of filaments separated from each other. 



Fig. 3. 



The researches of Kulliker on the intimate structure of tlio nervous 

 tissue are the most recent, and we subjoin his general account of the 

 nerve-fibres as given in the translation of his ' Histology ' by Messrs. 

 Busk and Huxley : 



"The Nerve-Tubes, or Fibres, also termed primitive tubes, or primi- 

 tive fib-es of the nerves, are soft, fine, cylindrical filament*, having a 

 diameter of O'OOOS"' O'Ol'"; they constitute the principal part of 

 the nerves and of the white substance of the central organs, although 

 they are not wanting in the greater part of the gray substance of the 

 latter and iu the ganglia. When examined in the recent state and by 

 transmitted light, they appear as clear as water, transparent, and 

 with simple dark contours ; by reflected light glistening, opaline, 

 ike fat, in larger quantities together, white, and for the most part 

 ;heir appearance does not indicate that they are composed of different 

 constituent parts. But it is readily seen upon the application of 

 various methods, that they consist of three entirely distinct com- 

 lonent structures, viz. of a delicate coat, and a viscid fluid, in the 

 centre of which is a soft but elastic fibre. 



" The Coat, or Sheath, of the Nerve-Fibres (Limitary Membrane, 

 Valentin) is an excessively delicate, flexible but elastic, perfectly 

 itructureless, and transparent membrane, which, in quite unaltered 

 nerve-fibres, except in certain situations, is altogether invisible. But 

 on the application of suitable reagents, at least in the thicker fibres 

 of the nerves and of the central organs, it comes readily into view, 

 corresponding, in its chemical characters, in all essential particulars, 

 with the sarcolemma of the muscular fibres. In the finest fibres of 

 rhe peripheral as well as of the central nervous system, the existence 

 of this membrane has not yet been demonstrated, and it must conse- 

 quently, for the present, be left undecided whether these fibres possess 

 sheaths or not. 



" Within the structureless slieath lies the Nerve-Mc Julia, or Pulp 

 Medullary Sheath of Rosentlml and Furkinje ; White Substance of 



