BY DR. LAUDER BRUNTON. 457 



CHAPTER XXXVII. 



DIGESTION. 

 SECTION I. SALIVA AND ITS SECRETIONS. 



72. Mode of obtaining Mixed Saliva. To obtain a 

 sufficient quantity of human saliva for examination, the secre- 

 tion of the salivaiy glands must be stimulated artificially. 

 For this purpose anj' of the mechanical or chemical stimuli to 

 be mentioned in 85 may be used. To avoid the risk of the 

 saliva becoming altered by mixture with the substance used 

 to quicken its secretion, the mechanical stimuli should be pre- 

 ferred. There is no objection, however, to the employment of 

 ether vapor. 



** 73. Examination of Mixed Saliva Appearance. 

 Saliva is transparent or opalescent. It sometimes deposits a 

 white precipitate almost immediately after it has been col- 

 lected. When poured from one vessel to another, it is seen 

 to be more or less viscid, in consequence of which it is gen- 

 erally filled with air-bubbles. If none are present, they are 

 readily produced \)y blowing into the liquid through a 

 narrow glass tube, when it is seen that they take a long time 

 to subside. If the saliva is allowed to stand long, a thin pelli- 

 cle of carbonate of lime forms on its surface. Microscopical 

 K.i'nmination. Saliva contains numerous air-bubbles, pave- 

 ment epithelium cells from the mouth, and round cells (sali- 

 vary corpuscles) resembling lymph corpuscles, within which 

 are numerous granules in constant movement. 



** 74. Determination of the Amount of Water and 

 of Solids. Take a small porcelain crucible with a lid, dry it 

 in an air-bath at 100 C., put it under a bell-jar over a dish 

 containing strong sulphuric acid till it is quite cool, then 

 weigh it immediate!}' and note its weight carefully. After 

 weighing it, replace it in the air-bath for another hour, cool it 

 and weigh it again as before. If the weight is less the second 

 time than the first, the process must be repeated till no further 

 loss of weight occurs. Introduce some saliva into it and 

 weigh again. The amount of saliva used is ascertained by de- 

 ducting the weight of the crucible alone from the weight of 

 the crucible and its contents, thus : 



