SALTS 



All living matter contains salts, chiefly the chlorides, sulphates 

 and phosphates of Xa, K, Ca, Mg and Fe. The role of the salts in 

 the organism will be considered under the physiology of the various 

 tissues. 



EERHIENT ACTION ENZYblES 



In the preceding experiments the breaking down of biological 

 compounds has been studied from the point of view of pure chem- 

 istry. The compounds were split by boiling acids or alkalies. That 

 similar decompositions may be effected at low temperatures by 

 substances present normally in living tissues is shown by the fol- 

 lowing experiments. 



It is very essential in these experiments that the temperature 

 be as near that indicated as possible. 



I. HYDROLYZING ENZYMES. 



A. INVERTING FERMENTS. IXVERTASES. 



80. Iiircrtasc. Thoroughly grind up one-half of a cake of yeast 

 with sand and water in a mortar. Filter. Test the filtrate for 

 sugar with Fehling's sol. Any sugar in yeast? Then mix equal 

 volumes of the yeast extract and cane sugar solution and keep at 

 40 for 10 or 15 minutes. Then test with Fehling's solution. 

 Result ? Conclusion ? Invertase may similarly be demonstrated in 

 the intestinal mucosa. 



I'). AMYLOLYTIC OR DIASTATIC FERMENTS. AMYLASES. 



81 A. Plant Diastase. Crush thoroughly about 5 gins, of ger- 

 minating barley with sand in a mortar with a little water. Filter. 

 Then mix the filtrate with 10 cc. of starch paste, warm to 40, and 

 keep in water bath at 40 for an hour. Note any change in the 

 character of the liquid. Test with iodine and Fehling's solution. 

 Note the taste of the resulting liquid. Explain these results. Com- 

 pare with a control in which the extract was boiled before incubating 

 with starch. 



8 1 B. Saliz'ary diastase. Ptyalin. Collect a few cc. of saliva 

 into a beaker ( flow of the secretion may be accelerated by 

 chewing paraffin ) ; dilute the saliva with about 5 volumes of water ; 

 filter. Make the following mixtures : A. 5 cc. of equal volumes dilute 

 starch paste and saliva ; B. the same, using saliva that has been pre- 

 viously boiled; C. the same mixture as A -)- 5 drops io f / f HC1 ; D. 



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