ON THE LYMPHATIC SYSTEM. 169 



character of the alveoli is easily ascertained^ owiug to their com- 

 paratively slightly convoluted nature ; in the serous or albu- 

 minous salivary glands, however, this tubular and branched 

 character, although existing to the same extent as in the others, 

 is nevertheless not so conspicuous, owing to the alveoli being 

 very close and raucli convoluted. Hence, in a thin section the 

 same tube will be found cut several times in succession, most of 

 the tubes appearing cut transversely, few also obliquely. But 

 making a thick section through a moderately hardened gland, or 

 making a section through a fresh gland, and teasing this 

 slightly out, the tubular, branched, and convoluted nature of the 

 alveoli can be ascertained beyond any doubt. A representation 

 of the shape and nature of the alveoli of the albuminous salivary 

 glands (})arotid), as given by Heidenhain in fig. 3 in the article 

 several times quoted, is taken from a gland excessively shrunk ; 

 it does not by any means correspond to the natural state of the 

 alveoli. The parotid of the dog, the parotid and the submaxil- 

 lary of the rabbit, the submaxillary of man, when not exces- 

 sively hardened by spirit, when prepared with great care in 

 diluted alcohol (two parts of methylated alcohol and one part of 

 water), or in the mixture of chromic acid and spirit, above men- 

 tioned, or in a ^ p. c. solution of chromic acid, shows the 

 tubular, branched, and convoluted nature of the alveoli with 

 sufficient distinctness. In all albuminous or serous salivary 

 glands some of the alveoli are connected with one another from 

 place to place by very thin and short bridges, comjjosed of two 

 or three secretory cells. These bridges appear solid, no lumen 

 being perceptible in them, and it is probable that they are the 

 means of connecting neighbouring alveoli that lead into neigh- 

 bouring ducts. In the case of the muco -salivary glands I have 

 not seen these solid bridges ; here the alveoli are often more or 

 less constricted at the point of dividing, but the lumen is always 

 traceable through these constrictions. 



As regards the membrana propria of the alveoli in the dif- 

 ferent glands, there is nothing new that I can bring forward, 

 since this subject has been so thoroughly investigated by Boll, 

 Heidenhain, and Lavdowsky. But as regards the lumen and 

 the lining epithelium, the following points are worth mention- 

 ing : — The glands which I have examined can be arranged in the 

 following groups, taking the structure of the alveoli and the 

 intralobular ducts as the distinguishing characters. (a) Albu- 

 minous (serous) glands; the parotid of all animals j the sub- 

 maxillary of the rabbit ; the submaxillary of the guinea-pig; the 

 serous (major) portion of the submaxillary gland of man and 

 ape. {b) Compound mucous glands ; as such are considered 

 those in which the alveoli are lined with mucous cells, and out- 



