DIGESTION AND ABSORPTION 165 



(6) What tests may be used to determine the presence of gelatin 

 in the diffusate? Is gelatin diffusible? 



(7) The term proteoses is a general one and is used to designate 

 the mid-products of proteid digestion. The mid-product of albumin 

 digestion is albumose; of globulin digestion, globulose; of myosin, 

 myosinose; of vitellin, vitellinose; of casein, caseinose; or, in general, 

 of a proteid, proteose. 



Dialyzer (/) contains products of peptic digestion of proteids, 

 principally albumin. The progress of digestion was suspended at a 

 stage where there were present not only peptone, but mid-products 

 albumoses; or, to use the general term, proteoses. 



The problem which confronts us is to determine whether or not 

 proteoses are diffusible. 



(a) If peptone is diffusible, the diffusate will certainly contain pep- 

 tone. Do peptone and proteoses respond alike to all the general tests 

 for proteoses? 



(b) How may peptone be separated from the proteoses? What 

 single reagent is indicated in the case? 



(8) Demonstrate the diffusibility of peptone. 



(b) Milk. 



1. Materials. One litre of fresh whole milk; one litre of milk for 

 the preparatory steps of the demonstration. 



2. Preparation. (1) On the day before the demonstration fill a 

 500-c.c. open-mouthed cylinder with milk and put it in a cool place. 



(2) Two days before the demonstration weigh out 10 grams to 50 

 grams of whole milk in a platinum dish or in a thin porcelain dish. 

 Place it in a drying oven at 90 to 95 C., and dry to constant 

 weight. Record the dry weight. 



(3) Before the hour of demonstration burn the residue by bringing 

 the dish which contains the dry solids to a red glow in a Bunsen 

 flame, allowing ample access of oxygen. After the dish and the white 

 ashes have cooled in a desiccator, take the weight. All of these 

 weights should, of course, be taken upon an analytical balance. 



(4) Fill a dialyzer with diluted milk one day before the demon- 

 stration. 



3. Experiments and Observations. (1) What proportion of milk 

 evaporates at the temperature above suggested? It may be taken 

 for granted that this proportion represents practically the water of 

 the milk. 



(2) Of the solids of milk, what proportion is organic and what 

 proportion is inorganic? 



(3) What bases predominate in the ashes? 



(4) What is the character of the organic constituents of milk? 

 (a) Note that the milk that has been standing has separated into 



