cxlii NERVOUS SYSTEM. 



of union of two or more branches. Those which are found in several of the 

 fosss9 of the cranium and face are for the most part placed at the junction of 

 fine branches of the sympathetic with branches, usually larger, of the cerebro- 

 spinal nerves ; but they are generally reckoned as belonging to the sympa- 

 thetic syotem. 



The ganglia differ widely from each other in figure and size : those which 

 have been longest known to anatomists are most of them large and con- 

 spicuous objects ; but, by the researches of Kemak and others, it has been 

 shown that there are numerous small, or what might be almost termed 

 microscopic ganglia, disposed along the branches of nerves distributed to the 

 tongue, the heart, the lungs, and some other viscera ; also connected with 

 fine plexuses of nerves between the coats of the intestines. 



Ganglions are invested externally with a thin but firm and closely adherent 

 envelope, continuous with the fibrous sheath of the nerves, and composed of 

 connective tissue ; this outward covering sends processes inwards through 

 the interior mass, dividing it, as it were, into lobules, and supporting the 

 numerous fine vessels which pervade it. A section carried through a ganglion, 

 in the direction of the nervous cords connected with it, discloses to the uak<>d 

 eye merely a collection of reddish-grey matter traversed by the white fibres 

 of the nerves. The nervous cords on entering lay aside their investing 

 sheath and spread out into smaller bundles, between which the grey gang- 

 lionic substance is interposed ; and their fibres are gathered up again into 

 cords, furnished with sheaths, on issuing from the ganglion. The micro- 

 scope shows that this grey substance consists of nerve-cells and fibres with 

 supporting connective tibsue. The nerve-cells, or ganglion-globules, have 

 mostly a round, oval, or pyriform figure (figs. LXXVIL, LXXXII; and LXXXIII.). 

 They are inclosed in capsules formed of a transparent membrane with 

 attached or imbedded nuclei. 



Of the relation between the nerve-fibres in a ganglion and the ganglion-cells, 

 it may be stated that many fibres pass through without being connected with 

 the cells, but that every nerve-cell is connected with a fibre or with fibres. 

 According to Dr. Beale, each cell is connected with, at least, two fibres, 

 which, on reaching the nervous bundle in which they are distributed, run in 

 opposite directions (fig. LXXXII). One of the fibres is straight, usually of 

 tolerable size, and connected with the cell at one spot like a stalk in pyri- 

 form cells at the small end. The other, usually smaller, begins or is 

 attached at some distance from the insertion of the first, and makes several 

 turns on the surface of the cell, but within its capsule, which are continued 

 as spiral coils round the straight fibre, and then the two part company and, 

 apparently, run in opposite directions in the nervous bundle in which they 

 mingle. 



The spiral fibre bears large oblong nuclei along its course. These are seen on its 

 spiral turns upon the surface of the cell, and some, at the commencement of the 

 fibre, seem to be beneath the surface. It may be single from the first, or begin by 

 two or more filaments which join at some distance from the cell. Both fibres in- 

 crease in size as they proceed. They have at first the character of pale fibres (or axis- 

 cylinders), then one ot them generally the straight one, but it may be the other 

 at a short distance from the cell acquires a medullary sheath and becomes a dark 

 bordered fibre. At the same time it cannot be positively said that both fibres may 

 not become dark bordered, or both continue as pale fibres. The spiral fibres may 

 make more or fewer coils, and Dr. Beale thinks they are more numerous in 

 older cells for in some cases the smaller fibre (answering to the spiral one 

 elsewhere) is not coiled ; and the cells in such cases he considers to be young or 

 recently formed. 



