1835.] Species of Minerals containing Barytes. 375 



Sulphate of barytes and strontian are met with combined 

 in other proportions. I have seen three other species 

 described, but not having any of them in my cabinet, I have 

 not had it in my power to subject them to analysis. But 

 they have been analyzed by Dr Turner, and M. Gruner of 

 Hanover, and found composed of 



atoms, atoms, atoms. 

 Sulphate of barytes . . 1 - - 2 - - 5 

 Sulphate of strontian . . 5 - ' - 7, - - 2 



Article VI. 



On Human Saliva. By C. G. Mitscherlich. 

 (Poggendorff's Annalen, xxvii. 320.^ 



A most important object in the analysis of animal secretions 

 is to obtain them in a pure state. In the case of the saliva 

 it is obvious that there are numerous difficulties in the way 

 of procuring that fluid free from the substances which may 

 accidentally find their way into the mouth, either from the 

 food after mastication, from the oesophagus, or from the 

 mucus surfaces. In order to avoid the mixture of foreign 

 matter which it must necessarily meet with in the mouth, 

 the best method would be to procure it externally from the 

 parotid gland, either by means of an artificial incision, or 

 during the occurrence of a salivary fistula. It was in the 

 latter way that Mitscherlich obtained the saliva which he 

 subjected to examination. The saliva flowed out by an 

 opening half a line in diameter, at the third grinder of the 

 upper jaw, on the left side, the mouth of the parotid 

 duct being completely closed up. The patient, who was 

 about 41 years of age, was not much affected, so far as 

 regarded his general health, except that some degree of 

 emaciation was present. Digestion remained regular. The 

 urine was acid ; the perspiration natural, and the dejections 

 as usual. 



The method hitherto employed to determine the quantity 

 of saliva secreted by the glands, was to estimate that con- 

 tained in the mouth, a mode which was liable to great 

 objections ; but when the saliva of the parotid gland was all 

 evacuated by an opening in the cheek, the proportion of 

 the secretion under different circumstances was easily ascer- 

 tained. 



