12 FERMENTS 



toxins, may be divided into two groups the endoenzymes 

 and the exoenzymes. The former appear to be the result 

 of the functional activity of the cell, and to be so closely 

 associated with the tissues that they seldom appear in the 

 fluids of the body in anything but small quantities. Vernon 

 points out, however, that certain of these endoenzymes, 

 such as maltase, are elaborated in larger quantities. The 

 exoenzymes, like the exotoxins, are set free much more 

 freely, and may be thrown out into the fluids in consider- 

 able amounts whenever they are required : ' Probably 

 the endoenzymes and the exoenzymes are formed and are 

 bound up in the tissues in a similar manner, only the linkage 

 binding the exoenzymes is more readily snapped under an 

 appropriate chemical or nervous stimulus than that binding 

 the endoenzymes.' Both forms appear to be elaborated 

 in larger quantities during increased functional activity 

 of the tissues by which they are formed, the endoenzymes, 

 on the one hand, being stored up in the cells, the exoenzymes, 

 on the other, readily making their way into the fluids 

 surrounding the tissues. 



In the blood there are diastatic enzymes, e.g. amylase 

 which converts starch into dextrin and maltose, and a 

 glucase or maltase which converts these products into glu- 

 cose : indeed, it is maintained that there are several of 

 the amylase group. Corresponding to these, numerous 

 antibodies of various types are also probably present in 

 the blood. 



2. Organised or formed ferments, such as yeast, myco- 

 derma vini, moulds, and bacteria, are living vegetable 

 organisms of parasitic habit. 



The reduction of complex carbon compounds into simpler 

 forms is the work of both classes of ferments. Their effects 

 are produced, it is believed, in one of two ways : (1) By 

 abstraction of water, as in the conversion of starch into 

 sugar, or the splitting up of glucosides changes chiefly 

 effected by enzymes, and analogous to the effects of heat in 

 conjunction with diluted mineral acids or alkalies. (2) The 

 breaking up of the fermentible body is sometimes effected 

 by transfer of oxygen from its hydrogen to its carbon, as in 

 alcoholic and lactic fermentations, and in putrefactive 



