500 SALIVA. 



3. Lymph. 



The lymph in the lymphatics is a clear, pale yellow 

 liquid, in which drops of fat and colorless globules of 

 about the size of the blood-corpuscles may be detected 

 by means of the microscope. It contains for the 

 greater part fibrino-plastic protein compounds, but in 

 very varying quantities, and sometimes they are en- 

 tirely wanting. When they are present, the lymph 

 coagulates rapidly when removed from the vessels, 

 forming a clear gelatinous mass, which incloses the 

 lymph-corpuscles. The liquid which separates from 

 the fibrin contains albumen and the salts of the blood. 



During fasting, only lymph is contained in the 

 chyle-vessels of the intestinal canal ; during digestion, 

 however, albuminates, fats, etc., from the food enter 

 this lymph, and it becomes what is called chyle, which 

 is then carried into the blood through the thoracic 

 duct. 



4. Saliva. 



The saliva is secreted by six salivary glands, and 

 emptied into the cavity of the mouth through the ex- 

 cretory ducts during chewing or in consequence of 

 irritation. Mixed with the mucus of the mouth, it 

 shows very small, clear corpuscles under the micro- 

 scope ; it is generally slightly alkaline. When dried, 

 it leaves behind about 1 per cent, of solid ingredients. 

 These consist of mucus, several salts, traces of albu- 

 men and organic substance (ptyaline), that has not 

 been separated nor analyzed. It is difficultly soluble 

 in water, insoluble in alcohol ; the solution does not 

 become turbid by boiling, and the ptyaline is not pre- 

 cipitated by acids nor metallic salts. At 70 it con- 

 verts starch into dextrin and sugar. The most re- 

 markable ingredient of the solid residue is a small 

 quantity of potassium sulphocyanide, which can be 

 extracted by means of alcohol. 



The so-called tartar of the teeth, which is deposited 

 from the saliva, consists of bone-earth, held together 



