ORIGIN AND COURSE OF NERVES. 



479 



adniaxillary glands (Klein) have been found, so far as they have been 

 investigated, to be mucous glands. 



One or two points with regard to the structure of the alveolar cells, 

 which bear- upon questions we have to consider later, we may also 

 mention. 



In all salivary alveolar cells there are found, though with very 

 different degrees of distinctness, more or less spherical granules, destined 

 in an altered or unaltered condition to become part of the secretion. 

 Whether the cell substance, in which the granules are embedded, has 

 or has not a definite structure, we cannot decide with certainty; this 

 cell substance may be what we speak of as granular structureless 

 protoplasm ; or it may consist of two parts, a protoplasmic part form- 

 ing externally a boundary layer, except perhaps towards the lumen, 

 and internally a delicate network ; and another part between the net- 

 work and the granules, which in some cells may be of an albuminous 

 and in others of a mucous nature. 



Every gland has its own distinctive histological features, implying a 

 distinctive chemical character in the substance it secretes. In addition, 

 secreting cells of obviously different nature often occur in the same gland. 

 Thus, in the submaxillary gland of the rat, there is an ordinary albuminous 

 portion, and running through this are tubes, in bold curves, consisting of cells 

 with large granules, which sometimes leave an outer clear zone. And in the 

 submaxillary gland of the rabbit, the first cells of the alveoli, and the terminal 

 ductules, have in the fresh state conspicuous granules, differing widely from 

 the faint granules of the rest of the cells in the alveoli. 



OKIGIN AND COURSE OF THE NERVES TO THE SALIVARY GLANDS. 



All the salivary glands are supplied with nerve-fibres from two 

 sources. They receive nerve-fibres, on the one hand, from the medulla 

 oblongata, by way of some cranial nerve ; and, on the other hand, from 

 the spinal cord, by way of the cervical sympathetic. 



The cranial nerve contains many, the sympathetic nerve comparat- 

 ively few, secretory fibres. The cranial nerve contains vaso-dilator, 

 and the sympathetic nerve contains vaso-constrictor fibres for the small 

 arteries of the glands. There is, at present, no evidence worth con- 

 sidering that the cranial nerves have vaso-constrictor fibres for the 

 glands, or that the sympathetic nerve has vaso-dilator fibres for them. 



The chorda tympani. and the nerve-cells with which it is 

 connected. The submaxillary, the sublingual glands, and the glands 

 of the tongue, receive secretory and vaso-dilator fibres from the chorda 

 tympani. The chorda tympani arises from the seventh nerve ; it leaves 

 this in the Fallopian canal, runs across the tympanum, and joins the 

 lingual branch of the third division of the fifth nerve. The nerve thus 

 formed may be called the chordo-lingual ; it extends roughly up to the 

 dorsal edge of the sublingual gland ; here nearly all the fibres for the 

 submaxillary gland, and about half of those for the sublingual gland, 

 leave the lingual fibres, generally in four or five delicate strands, lying 

 close together. These strands, with the tissue around them, are easily 

 dissected out as a single bundle, and the bundle of nerve strands is 

 called the chorda tympani, although it is a part only of the chorda 

 tympani proper. The chorda tympani curves backwards towards the 



