610 THE DIGESTIVE TRACT. 



each other. The pancreas has the smallest acini, and here the 

 epithelia are found coarsely granular, even homogeneous toward 

 the structureless layer. Some observers have erroneously claimed 

 that this gland belongs to the tubular variety. The ducts of all 

 salivary glands are lined by columnar epithelia. The pancreatic 

 duct is provided with acinous mucous glands. The columnar 

 epithelia, in the smaller ducts chiefly, show a delicate longitudinal 

 striation, which is most distinctly marked in the portion of the 

 epithelium nearest the structureless layer. The significance of 

 this striation will be dwelt upon in the article by H. B. Millard, 

 treating of the epithelia of the kidney. In the tubules of the 

 ducts inosculating with the acini, the epithelial lining shows 

 slight differences in different salivary glands. 



Saliva, transferred to the slide in a perfectly fresh condition, and covered 

 with a thin covering-glass, is an excellent specimen for the study of bioplasson 

 bodies. Besides flat epithelia from the oral cavity and a varying number of 

 leptothrix, we find the salivary corpuscles *. e., the former tenants of gland- 

 ular epithelia. These are nucleated plastids exhibiting the reticular struct- 

 ure and amoeboid movements, at usually the ordinary temperature of the 

 room. To study the form changes, it is advisable to sketch on paper from the 

 beginning of the investigation. Large, swelled corpuscles, with pale, vesic- 

 ular nuclei, may also be found, containing granules which, being the remnants 

 of the torn reticulum, are in an active so-called " molecular" motion. The 

 number of such hydropic corpuscles increases with the duration of the obser- 

 vation under the microscope. At last both the active and hydropic corpuscles 

 burst, and masses of detritus or clusters of granules result. The nuclei of the 

 flat oral epithelia also exhibit the reticular bioplasson structure, and are 

 obviously endowed with vitality, which endures for some time after the horny 

 change of the rest of the epithelium has taken place (Strieker). 



In thrush (see page 44), the whitish patches consist of an aggregation of 

 leptothrix, oiidia, and scanty-chambered mycelia ; in short, the constituent 

 elements of mildew. 



In catarrhal stomatitis, the number of salivary corpuscles is considerably 

 augmented, and the amount of the bioplasson they contain increased, as 

 shown by their coarser granulation. Such corpuscles attain all the appear- 

 ances of pus-corpuscles, and may be so termed. Stringy threads of mucus are 

 also found in even slight degrees of inflammation of the mucosa, caused by 

 mucous transformation of bioplasson before its ejection from the epithelia, 

 and coalescence of a number of mucous globules. A small amount of blood 

 is usually found intermixed. 



In croupous inflammation, the grayish white, so-called "pseudo-membran- 

 ous '! formations covering the swelled and considerably hypersemic mucosa, 

 consist of a fibrinous exudation, which under the microscope appears as a 

 felt-work of sometimes narrow, sometimes broad, granular fibrils. (Repre- 

 sented on page 516, Fig. 212.) In the meshes of this irregular felt- work scanty 

 bioplasson bodies are found, which may be considered either as nuclei of 

 former epithelia, destroyed in the production of the croupous exudate, or as 



