236 SECRETING GLANDS. 



a collection of the smallest lobules, united by connective tissue and 

 vessels, forms one of the next size, which, too, has its larger branch of 

 the duct, formed by the junction of the ramuli belonging to the ulti- 

 mate lobules. In this way, the whole gland is successively made up, the 

 number of its lobules and of the branches of its duct depending on its 

 size ; for whilst some glands of this kind, like the parotid and pancreas, 

 consist of innumerable lobules, connected by a large and many-branched 

 duct, others, such as the duodenal glands of Brunner and many mucous 

 glands, are formed of but two or three ultimate lobules, or even of a 

 single one, with a duct> minute in size and sparingly branched, to 

 correspond. In fact, a small racemose gland resembles a fragment of a 

 larger one. 



The ultimate saccules of a racemose gland or alveoli, as they are 

 commonly termed, are almost entirely filled by the secreting cells, only 

 a small cavity being left in the centre communicating with the excretory 

 duct. It would appear, however, that in many cases at least, minute 

 canals lead from the central cavity between the cells, and these 

 may aid in the conveyance of the secretion of the latter towards the 

 duct. It is doubtful whether these intercellular channels have proper 

 walls or are merely formed by the juxtaposition of grooves on the 

 adjacent sides of the cells. Further — the flattened cells which compose 

 the basement-membrane have delicate lamellar processes extending 

 between the alveolar cells, among which they appear to form a susten- 

 tacular network (Boll, Ebner). 



A great many compound glands, yielding very different secretions, 

 belong to the racemose class. As examples, it will be sufficient to 

 mention the pancreas, the salivary, lachrymal, and mammary glands, 

 with the glands of Brunner already referred to, and most of the small 

 glands which open into the mouth, fauces, and windpipe. From the 

 description given of their structure, it will be understood why the term 

 " conglomerate glands " has been applied especially though not exclu- 

 sively, to this class. Their smallest lobules were called acini, a term 

 which has also been used to denote the saccular recesses in the lobules, 

 and indeed the word acinus, which originally meant the seed of a. berry 

 or the stone of a gi'ape, or sometimes the grape itself, has been so 

 vaguely applied by anatomists, that it seems better to discard it alto- 

 gether. 



Of the tubular compound glands, the most characteristic examples 

 are the testicle and kidney. In these the tubular ducts divide again 

 and again into branches, which, retaining their tubular form, are greatly 

 lengthened out. The branches of the ducts are, as usual, formed of a 

 limitary or basement-membrane {memhrana propria), lined by epithe- 

 lium, and in contact, by its opposite surface, with capillary blood- 

 vessels. By the multiplication and elongation of the tubular branches 

 a vast extent of secreting surface is obtained, whilst to save room, the 

 tubes are coiled up into a more or less compact mass, which is traversed 

 and held together by blood-vessels, and sometimes, also, divided into 

 lobules and supported, as in the testicle, by fibrous partitions, derived 

 from the inclosing capsule of the gland. In consequence of their 

 intricately involved arrangement, it is difficult to find out how the 

 tubular ducts are disposed at their extremities. It seems probable, 

 however, that some are free, and simply closed without dilatation, and 

 that others anastomose with neighbouring tubes, joinmg with them in 



