424 THE SALIVARY GLANDS, BY E. F. W. PFLUGER. 



cavity is of very variable calibre, and may attain the mean 

 diameter of a salivary cell, but may be also both extraordinarily 

 fine (1 2 fj) and several in number in one and the same alveo- 

 lus. The central canal gives off, as I have found, in conjunction 

 with Mr. Anton Ewald, student in medicine, extremely fine 

 tubuli (salivary capillaries), which penetrate between the sali- 

 vary cells and also between the tunica propria and the epithe- 

 lial cells ; so that these, like the cells of the liver, are surrounded 

 by tubuli that can be injected with Prussian blue, and appear 

 to proceed from one alveolus to another. The parietes of the 

 tubes, composed in general of a single layer of cells, are invested 

 externally by an extremely fine, and when fresh, completely 

 structureless membrane, called the membrana propria. The 

 existence of this may be demonstrated by macerating the fresh 

 submaxillary gland with distilled water, when the membrane 

 becomes raised from the epithelium, often to a considerable dis- 

 tance, in the form of a hyaline vesicle. Recently the presence 

 of a membrana propria in glands generally has been called 

 into question, and especially by Schliiter,* in the case of. 

 the salivary glands. In order to exhibit it I would recom- 

 mend the pancreas of the rabbit to lie for four days in iodized 

 serum of a light sherry colour, and subsequently for two days 

 in five cubic centimeters of diluted chromic acid, containing one- 

 fiftieth per cent. By an action that is clearly of a digestive 

 nature, the epithelial cells are in part detached, and obviously 

 lie in a wide hyaline sac which they by no means fill. This 

 appearance will incontestably demonstrate the existence of a 

 membrana propria, forming a closed and continuous membrane. 

 A question of a totally different nature is whether this 

 membrane may be regarded as being composed of flat cells 

 fused or coalesced together. According to Bollf and Kolliker, 

 it is composed of anastomosing connective-tissue cells that 

 form a reticulum in which the alveolus lies as in a cavity of 

 trellis or wicker-work. However plausible this view may 

 appear on a priori grounds, there are facts which can scarcely 



* Disqisit. Mic. et Phys. de Gland. Salivar. Vratisl, 1865 ; Inaug. Diss. 

 t Franz Boll, Ueber den Bau der Thrdnendriise im Archw f. Mikroskop. 

 Anatomie, Band iv., 1868, p. 146. 



