96 EEPOET OF THE COMMISSIONER OF AGKICULTUR13. 



Before proceeding further with the microscope a portion of the sam- 

 liles is usually submitted for examination to a test "with sulphuric acid. 



While these two simx)lo tests will always distinguish true oleomarga- 

 rine from butter their result is less decisive in the case of butterine, 

 owing to its containing a considerable proportion of butter. Hence it 

 is often necessary to subject what iii^pears to be genuine butter to a 

 closer examination. When this is the case, resort is again had to the 

 microscope, iirst removing any salt i)resent by pressing a portion of the 

 substance through the meshes of tine cambric muslin,* then mounting 

 the specimen with as little friction as possible, and viewing it by })lain 

 transmitted light under a power of about 75 diameters. If well-defined 

 crystals of fatare present they are at once seen. Should the crystals 

 be in the amorphous state they may not be seen in this way. I then 

 resort to polarized liglit when very minute fatty crystals are at once 

 detected, if present, provided the polarizer is rotated until its face angle 

 is at right angles with tliat of the analyzer. Push the polarizer down 

 as lowas the stand will permit. By this means a darker ground is 

 produced, and the bright specks or lis;ht shades of fat will appear in 

 view over the dark ground. 



When amor])hous crystals are detected by this means it is desirable to 

 ascertain whether they are of beef or lard. 



Boil about 1 ounce of the substance and cool it slowly.. The next 

 step is to examine under the microscope a portion of it thus prepared. 

 To accomplish this it will be necessary to ])repare by any of the well- 

 known means on a glass slide of 1 by 3 inches, a varnish ring one hun- 

 dredth of an inch in thickness when dry. Put a single drop of any 

 thick, transparent oil within the varnish circle and place in contact with 

 the oil a very small ])ortion of the suspected substance. Use a point, 

 such as that of a pin or needle, to separate the lioatiug fatty substance 

 into very fine granules (crystals). Place a suitable glass disk or 

 "cover" over the oil and press it gently down so that it will come in 

 contact with the varnish ring, which should receive one coat of varnish 

 just before the slide is used and Should bo of sufficient thickness to 

 protect the crystals from pressure by the cover. The object may now 

 be viewed bj- plain transmitted light. If the crystals exhibit a well- 

 defined stellar form, such as Figs. 13, 14, or 15, the substance is lard; 

 if such as 18 it is beef iat. The latter should be viewed with the high 

 powers, so as to observe the biserrated form of the individual spines of 

 which the perfect crystal consists. If butter crystals are present, they 

 may be of one or both fornis, globular or rosette. (See Pigs. 7, 8, 9, and 

 r>, Plate 1.) 



In Plate I, Fig. 1 represents the crystals of boiled butter as seen bj 

 a pocket lens: Fig. 2, highly magnified crystals of butter from a breed 

 of Shorthorn, Devon, and Tennessee native cattle, showing the " cross" 

 under polarized light; Fig. 3, crystals of butter from a breed of pure 

 Alderney ; Fig. 4, highly magnified crystals of Tennessee butter under 

 j)!ain transmitted light; Fig. 5, a budding crystal of Tennessee butter; 

 Fig. G, the indented crystal peculiar to Tennessee butter of this grade; 

 Fig. 7, a crystal of butter from Huron County, Ohio; Fig. 8, the rosette 

 form of secondary crystallization of butter as seen under polarized light 

 and selenite plate; Fig. 9, secondary crystallization of butter under po- 

 larized light without selenite plate^; Fig. 10, a crystal of butter under 

 polarized light and selenite plate ; Fig.ll, a crystal of oleomargarine 

 under polarized light, in which sample a large proportion of butter is com- 

 bined with lard, the presence of butter being indicated by the "cross" 

 and that of lard by " spines " j Fig. 12, the same crystal under polarized 



