Epithelial Tissues. 



23 



The majority of multicellular glands conform to one of two 

 types, namely, the tubular gland, in which the secreting portions are 

 of uniform calibre, and the acinous or alveolar gland, in which the 

 secreting portions are sacculated (Fig. 3, A). Both types occur in 

 simple, little branched and greatly branched conditions (Figs. 3, B, 4). 



Cutaneous glands of two types are commonly present in 

 mammals in association with the hairs, namely, sudoriferous or 

 sweat-glands, which are glands of the tubular type, and sebaceous 

 glands, which are of the acinous type. In the rabbit, glands are 

 absent from the general surface, but are found in special situations, 

 as, for example, in connection with the hair follicles ot the lips, 

 the internal surface of the ear, and the 

 external genital organs. The inguinal 

 glands comprise both tubular and acinous 

 portions. The mammary glands of the 

 female are greatly modified cutaneous 

 glands of an acinous type. 



Apart from the mucus-secreting cells of 

 the general epithelium, the glands of the 

 alimentary canal comprise the important 

 but less elaborated glands of the wall, such 

 as the gastric glands of the wall of the 

 stomach; and the greatly elaborated, out- 

 standing glands which lie beyond the wall 



and are connected with the interior of the canal only through their 

 ducts. The latter comprise the oral glands, the liver, and the 

 pancreas. The oral glands include chiefly the submaxillary, 

 parotid, sublingual, and infraorbital glands — conspicuous 

 structures in the dissection of the surrounding portions of the head 

 and neck. Their ducts communicate with the cavity of the mouth. 



The secretion of the oral glands has important mechanical 

 1 unctions in moistening the comminuted food in preparation for 

 swallowing. It also contains ferments or enzymes, chiefly 

 ptyalin, which is capable of transforming starch in soluble materials, 

 though the digestive action is probably not exercised to a great 

 extent. Pancreatic secretion, on the other hand, has little or no 

 mechanical action, but its enzymes are of the greatest importance 

 in digestion. 



Fig. 4. From a section of 

 the parotid salivary gland of 

 the rabbit. A. Duct system in 

 relation to body of gland: g, 

 acini of gland body; d, inter- 

 lobular duct; B. Three indivi- 

 dual acini, highly magnified. 



