CHEMICAL BASIS <>F TIM: ANIMAL r.Dv. 



purest (') ftirni by Cohnheim. 1 His iin j tlntil i-mi<i<t-. in the addi- 

 tion of phosphoric acid to the saliva until it is strongly arid ; the 

 mixture is then neutralised by tin- careful addition of lime-v 

 whereupon a copious precipitate of phosphate of lime is formed. 

 This carries down with it a large proportion ..f tin- proteids which 

 an- present, together with all the ptyalin. On extraction of the 

 precipitate with a volume of water equal to that of the saliva 

 originally employed, the en/vme passes chiefly into solution, since 

 less thinly adherent to the precipitate than are the pro- 

 teids ; it may now be purified still further by rej>eating the above 

 process .nid finally precipitating with absolute alcohol. Prepared 

 in this way. the enzyme is obtained as a fine white amorphous 

 powder. Dissolved in water it is extremely active in hyilmlysin.. 

 starch, and the solution yields none of the reactions mo>t t ypieallv 

 rTiaracteristic of proteids. On these ^rounds it is asserted that 

 ptyalin is not a proteid, but the evidence is not conclude. 

 More recently this enzyme has been prepared as follows. 8 Saliva 

 is diluted with an eijual volume of water, and saturated with 

 neutral ammonium sulphate. The precipitate thus formed is 

 treated on the filter for five minuU's with strong ali-ohol. removed 

 from the filter, and further treated with absolute alcohol for one 

 or two days. It is now dried at 30, and yields, on extraction 

 with a volume of water equal to that of the original >al 

 solution which is actively zymolytic, and is stated to be five from 

 all proteid reactions. The hydrolytic activity of ptyalin is most 

 marked in neutral or nearly neutral solution 

 An amylolytic enzyme is found in urine. 4 



experiments have as yet established tin- existence of anv 

 of ptyalin (ptyalinogen). 6 



The amylolytic enzyme of the pancreas. 



The_. secret ion of the pancreas is even inure active than saliva 

 in_ejjerTingthe hydrolysis ot starch.'' This property is dejendent, 

 upon the ''presence In this secretion of an en/yme \\hich in many 

 closely resembles ptyalin, but d tilers from it markedly in 

 its greater power of effecting a more complete deconipnsition of 

 the_sUirch than can ptyalin. Under ordinary conditions the only 

 sugaF~Torniel by the action of ptyalin on -tardi is mall..-- . n. 



ver, the aetion is prolonged, small amounts of d> -\tros. 

 it is stated, also make their appeal -he re-ult of the fur- 



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