ZYMOLOGY FERMENTS AND FERMENTATIONS 225 



e. Fibrin ferment. This ferment causes the coagulation of blood. It 

 occurs in the blood of all animals excepting in "bleeders" in which it is 

 absent, a condition causing much trouble in checking hemorrhages result- 

 ing from even very trivial injuries and operations. It is supposed that 

 under certain conditions the fibrinogen is split into fibrin and globulin. 

 The fibrin and globulin can readily be separated, as is done in the manu- 

 facture of concentrated diphtheria antitoxin. There are many phases of 

 blood coagulation which are as yet not understood. Those interested will 

 find fuller discussions in modern works on human physiology and anatomy. 



f. Agglutinins and Precipitins. These problematical enzymes are 

 found in the blood of animals. The former cause the bacterial clumping 

 as in the Widal test for typhoid fever. The latter cause the formation of 

 precipitates in blood. Both are specific in nature and shall be more 

 fully discussed elsewhere. It is highly questionable whether these agents 

 should be classed as coagulating ferments. 



3. Starch Splitting or Sugar Forming Ferments. Under this head are 

 included those highly important ferments which act upon carbohydrates, 

 splitting them up into simpler compounds. The fermentations due to 

 these enzymes are simple hydrolytic processes, analogous to those caused 

 by dilute acids. One of the most common end products is glucose. 



The starch splitting ferments are widely distributed in the vegetable 

 as well as in the animal kingdom and they play a most important part in 

 domestic economy. They bear the same relationship to carbohydrates 

 that the proteolytic ferments bear to proteid substances. 



The activity of starch ferments is tested in various ways. Complete 

 digestion of starch is indicated by the absence of the iodine reaction. The 

 optical behavior of the substance undergoing fermentation is also an 

 indication as to the nature and identity of the ferment. Of interest is 

 the auxanographic method proposed by Beyerinck. If, for example, it is 

 desired to know if glucose has been formed, the substances is inoculated 

 with a fungus which will develop upon glucose (as Saccharomyces apicu- 

 laius) but not upon maltose. Fehling's test and other sugar reactions 

 may also be used. 



The saccharine substances formed vary in composition in the amount 

 of reduced sugar present, in the character and degree of polarization 

 (rotation), etc. 



The different starches as of rice, barley, wheat, potato, etc., do not 

 digest or ferment at the same rate at a given temperature. For example 

 at 50 C. diastase will digest 12 per cent, barley starch, 2 per cent, corn 

 starch and 29 per cent, malt starch; at 55 C., 5 per cent, potato starch, 

 53 per cent, barley starch and 58 per cent, malt starch; at 60 C., 52 per 

 cent, potato starch, 92 per cent, barley starch and 18 per cent, corn starch. 



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