88 PHYSIOLOGICAL CHEMISTRY. 



complete insolubility of the albuminous matters. The coagulum is then 

 dried, pulverized, treated with water to double the original volume of 

 the serum, and the watery extract filtered. The filtered solution con- 

 tains the ferment, and if added to a fluid containing fibrinogen will 

 cause its coagulation. 



5. Diastase. 



Diastase is a vegetable nitrogenous matter, produced in the germina- 

 tion of the cereal grains, and especially of barley, by which their 

 starch is converted into dextrine and sugar. It may be extracted from 

 malting barley with water, the concentrated watery extract being 

 precipitated by alcohol, and the precipitate dried and redissolved in 

 water. Its action is most rapid in a neutral menstruum and at mod- 

 erately warm temperatures, ceasing about 75 C. It is considered as 

 the representative of the sugar-producing bodies of this group, all 

 those having a similar action being designated as "diastatic" ferments. 



MTJCIFORM, GELATINOUS, AND SOLID ALBUMENOID SUB- 

 STANCES. 



The substances of this group are distinguished rather by their con- 

 sistency than by their active chemical or physiological properties. They 

 do not form part of the nutritious juices, like albuminous matters, nor 

 give rise to chemical transformations like the ferments. They have 

 reached their final stage in the constructive nutrition of the body, and 

 are useful in facilitating the mechanical movement of the parts, or in 

 holding the other ingredients of the tissues in a coherent mass. They 

 are not easily affected by chemical influences, and most of them show 

 great resistance to the action of ordinary alkaline or acidulated liquids. 

 As a rule, they constitute the organic part of the solid tissues. 



1. Mucine. 



There are various secretions in the body designated by the common 

 name of "mucus," and distinguished by a peculiar physical character 

 of viscidity and lubricity. This consistency is due to the presence of 

 mucine. It exists in all the varieties of mucus, some of which, like 

 those of the bronchial tubes and intestines, are nearly fluid, while 

 others, like that of the cervix uteri during pregnancy, are gelatinous 

 and semi-solid. It is also present in the synovia, the secretion of the 

 ^all-bladder, and the saliva of the submaxillary and sublingual glands. 

 The secretion of the mucous follicles of the mouth consists of it almost 

 exclusively. Like the albuminous matters, it contains carbon, hydro- 

 gen, nitrogen, and oxygen, but is destitute of sulphur. In pure water 

 it swells up without becoming liquid, but it is soluble in alkalescent 

 solutions, particularly in those of the alkaline earths, as lime-water and 

 baryta-water. It is not affected by boiling, but is precipitated by acetic 

 acid. It is thought to be held in solution in the mucous secretions by 

 their free alkali ; the varying consistency of the secretions being due 



