!8 2 NORMAL HISTOLOGY. 



The main nerve-trunks of the liver enter at the transverse fissure 

 in company with the blood-vessels and the lymphatics. The fibres 

 consist largely of the non-medullated, together with a smaller number 

 of the medullated variety. These nerves run within the interlobular 

 connective tissue in company with the hepatic artery. They may 

 be traced with certainty to the periphery of the lobule ; regarding 

 the exact mode of their ultimate distribution, however, nothing is 

 definitely known. Minute ganglia occur along the interlobular 

 trunks. 



The gall-bladder, or bile-sac, possesses walls composed essen- 

 tially of the same tissues as those of the larger bile-ducts, these consist- 

 ing of a mucous membrane supplemented by oblique bands of invol- 

 untary muscle and an outer fibrous coat. The mucosa is thrown 

 into minute folds or rugae, which unite and interlace to form a net- 

 work of ridges and give to the surface of the mucous membrane a 

 reticulated appearance. 



The blood-vessels, the lymphatics, and the nerves form net-works 

 within the mucosa, which usually terminate in the superficial or inner 

 layers of the tunica propria. 



THE ACCESSORY DIGESTIVE GLANDS. 



These include the salivary glands the parotid, the submaxillary, 

 and the sublingual and the pancreas. While in their quiescent, 

 immature condition all are similar, after full functional development 

 is attained the variation in the character of their secretions leads to 

 the recognition of two groups the serous and the mucous sali- 

 vary glands. Those of the serous type, regarded as the true sali- 

 vary glands, are represented in man and mammals by the parotid 

 gland and the pancreas. The mucous glands are best represented 

 in man and many animals by the sublingual, although the presence 

 of serous acini places this organ, strictly considered, within the cate- 

 gory of the mixed glands. 



The muco-serous or mixed glands are exemplified by the sub- 

 maxillary of man and many mammals (as apes, guinea-pig, etc.); 

 in other animals (as dog or cat) this gland is entirely mucous, while 

 in certain others (as the rabbit) it is a true serous gland. 



THE SALIVARY GLANDS. 



The parotid is a compound saccular or racemose gland, en- 

 veloped in a general fibrous capsule from which stout connective- 

 tissue septa penetrate the organ, dividing the gland into lobes. 

 These latter are subdivided by fibrous partitions into numerous lob- 

 ules, each of which, in turn, is composed of groups of the ultimate 

 saccules or acini. 



