470 ULTIMATUM STRUCTURE OF THE SALIVARY GLANDS. 



. . 



This nerve after being covered a short distance by the 

 gland, enters its substance, and forms there the plexus called 

 pas anserinus, so as to leave a portion of the gland on the inner 

 face of the nerve. The external carotid artery likewise traverses 

 the gland and is situated rather more exteriorly than the nerve, 

 so as to leave about one-third of the gland on its inner face. 

 Branches from the artery* are sent off in various directions 

 as it traverses the gland, to the face, and to the structure of the 

 gland itself. 



The duct of Steno, is very feebly attached to the surrounding 

 parts, and is accompanied by many branches of the middle 

 division of the facial nerves, and some small arteries which 

 supply its walls ; it is covered only by the skin, some adipose 

 tissue, by some fibres of the platysma myoides, and the 

 zygomaticus major which crosses it obliquely. Its general 

 diameter is about a line ; and it is very distensible. It will be 

 found, according to the rule laid down by Dr. Physick, 

 under a line drawn from the lobe of the ear, to the tip of the 

 nose. 



119. The duct is composed of two coats, one, 

 external, white, fibrous, and resisting; the 

 other, internal, is a mucous membrane, con- 

 tinuous with the lining membrane of the 

 mouth, and appears to differ from it only in 

 being paler. 



Fig. 119, is a microscopical representation 

 of the structure of a portion of the parotid 

 gland of a young infant, after it had been 

 minutely injected with mercury from the duct of Steno, by E. 

 H. Weber, of Leipzic. The small figure, to the right, is the 

 natural size of the piece magnified, in which the salivary ducts 

 were filled with the fluid to their very terminations. A branch 

 of the salivary duct, is seen on the right margin of this figure, 

 ramifying like the branch of a tree. These ramifications never 

 anastomose together, and are of much greater size than the 

 capillary blood-vessels. Each ramification, at its termination, 

 resolves itself into cells densely compacted together, like a 



