

DIGESTION 299 



It is impossible with our present knowledge to represent the entire 

 process by a chemical equation. If we look only to the final product, 

 the equation 



(C 6 H 10 6 ), + f H 2 = 2 (C^HoA,) 



Starch. Water. Maltose. ] 



or 



*+ 1 ' f~* T-T /^\ \ i r-rTT ^*\ ~f~* TT ^\ 



2^ 6 rt 10 u 5 ; a + #i 2 u = a^ l2 ki 2 2\j n 



will represent the change in natural and complete digestion. The 

 molecule of starch being taken as some unknown multiple, , of the 

 group C 6 H 10 O 5 , the first equation suits the case of a being an even 

 number, and the second that of a being an odd number. 



If we accept 4 per cent, as the minimum residue of unchanged 

 dextrin in the best artificial digestion, or, in other words, if we suppose 

 that of 25 parts of starch 24 are changed into maltose, and i remains 

 as dextrin, our equation, taking the dextrin molecule as a multiple b 

 of C 6 H 10 O 5 , will be : 



2 5(C 6 H 10 O 5 ) a + 1 2#H 2 O = 1 20 (C 12 H 22 O n ) + - (C 6 H 10 O 5 )$ 



Starch. Water. Maltose. Dextrin. 



for the case where - is a whole number. If y is not a whole 

 o b 



number, we should have to clear 'of fractions by multiplying both 

 sides by , where m is the greatest common measure of a and b. 



M 



We should thus get : 



Starch. Water. Maltose. Dextrin. 



It is a notable fact that amylolytic ferments are not 

 confined to the animal body. Diastase, which is present in 

 all sprouting seeds, and may be readily extracted by water 

 from malt, forms maltose and dextrin from starch. Its 

 optimum temperature, however, is about 65 C., while that 

 of ptyalin is about 40 C. 



"While a neutral or weakly alkaline reaction is not un- 

 favourable to salivary digestion, it goes on best in a slightly 

 acid medium (Kubel). But an acidity equal to that of a 

 *i per cent, solution of hydrochloric acid stops it completely, 

 although the ferment is still for a time able to act when he 

 acidity is sufficiently reduced. Strong acids or alkalies per- 

 manently destroy it. These facts show that in the mouth, 

 where the reaction is weakly alkaline, the conditions are 

 comparatively favourable to the action of the ptyalin. They 



