_d_. When butter fat is used to provide a source of "A" vitamine it is prepared as follows: Butter is melted in a flask on a water bath at 45°C. and then centrifugated for an hour at high speed. This results in a separation of the mixture into three layers: (a) Clear fat, containing the "A" vitamine and consisting of 82 to 83 per cent glycerides. This is siphoned off and provides the butter fat named in the diets, (b) An aqueous opalescent layer consisting of water and some of the water-soluble constituents of the milk. This is rejected. (c) A white solid mass consisting of cells, bacteria, calcium phosphate and casein particles. This is also rejected. _Osborne and Mendel's diet_ (Figures give the per cent of each ingredient in the diet) _________________________________________________________________________ | | | INGREDIENTS | VITAMINE FREE | CONTAINING A ONLY | _______________________________|_________________|_______________________| | | | | | | | | | I | II | III | IV | V | VI | VII | Purified protein as casein, | | | | | | | | lactalbumin, edestin, egg | | | | | | | | albumin, etc. . . . . . . | 18.0|18.0 | | 18.0| 18.0| 18.0| | or Meat residue . . . . . | | | 19.6| | | |19.6 | | | | | | | | | Carbohydrates in the form of: | | | | | | | | Starch . . . . . . . . . . . | 29.5| 54.0| 52.4| 29.5| 54.0| 54.0| 52.4| Sucrose . . . . . . . . . . . | 15.0| | | 15.0| | | | | | | | | | | | Fat in the form of: | | | | | | | | Lard . . . . . . . . . . . | 30.0| 24.0| 24.0| 15.0| 15.0| 15.0| 15.0| Butter fat . . . . . . . . . | | | | 15.0| 9.0| | 9.0| Egg yolk fat . . . . . . . . | | | | | | 9.0| | Cod liver oil . . . . . . . . | | | | | | | | | | | | | | | | Salts in the form of: | | | | | | | | Salt mixture I . . . . . . . | 2.5| | | 2.5| | | | or Artificial protein-free | | | | | | | | milk (Mixt. IV) . . . . . . | | 4.0| 4.0| | 4.0| 4.0| 4.0| or Protein-free milk . . . | | | | | | | | | | | | | | | | Roughage in the form of: | | | | | | | | Agar-agar . . . . . . . . . . | 5.0| | | 5.0| | | |