164 SPECIAL PHYSIOLOGY 



solutions (a) and (b) of the Fehlihg solution, but in the proportion of 

 nine parts of the sodic hydroxide solution (6) to one part of the cupric 

 sulphate solution (a), and add an equal volume of the distilled water 

 to the mixture. 



Tabulate results on the proteid series (a) to (g). 



(6) Subject each of the series of proteids (a) to (g) to each of the 

 following reagents, tabulating results: 



(I) Picric acid, saturated solution. 



(II) Absolute alcohol. 



(III) Mercuric chloride, saturated solution. 



(IV) Tannic acid, saturated solution. 

 (V) Silver nitrate, 10 per cent, solution. 



(VI) Ammonium sulphate, saturated solution. 

 On which of the proteid solutions would one get a precipitate with 

 silver nitrate independent of the presence of proteid? 



(7) To Separate Peptone from Other Proteids. It will have been noted 

 that ammonium sulphate precipitates all proteids except pure pep- 

 tone. If one has peptone mixed with proteoses and unchanged pro- 

 teids, one may demonstrate its presence by precipitating out the 

 other proteids and then demonstrating by such a test as the Biuret 

 test the presence of a proteid in the clear filtrate; that could be 

 nothing else than peptone. 



Test commercial peptone in this way and determine whether any 

 appreciable proportion of it is peptone. 



(8) The Diffusibility of Proteids. Fill seven dialyzers with proteids 

 above studied. On the following day test the diffusates for proteids. 



IV. (a) DIFFUSIBILITY OF PROTEIDS. (b) MILK. 

 (a) Diffusibility of Proteids. 



1. Materials. The seven dialyzers filled at the end of the pre- 

 vious demonstration. 



2. Experiments and Observations. (1) What reagent may best 

 be used to determine whether or not any of the egg albumin has 

 diffused through the animal membrane? 



(2) How may one determine whether or not any of the salts of the 

 egg albumin have diffused through the membrane? 



(3) In the case of the saline solution of myosin (6), of syntonin (c), 

 and of acid albumin (d), is there any contraindication against silver 

 nitrate as a reagent to determine whether proteid has diffused? 



(4) What tests would be most reliable in these cases to detect the 

 presence of proteid in the diffusate? 



(5) Would a trace of proteid in the diffusate necessarily demon- 

 strate the diffusibility of these proteids through the walls of the 

 alimentary tract? If not, why not? 



