REPORT OF THE CHEMIST. 279 



In lard are seen polyhedral cells, arising from the compression of 

 the fatty globules. In impure lard are also seen the remains of cells 

 and adipose tissue. Fresh butter shows some long and delicate 

 needles of margarine (?), united in bundles and grouped in various 

 ways. When the butter is melted these needles diminish in length 

 an(l become grouped round a central point. I have mentioned these 

 descriptions especially for the purpose of calling attention to the fact 

 that in the illustrations of the microscopic appearance of butters and 

 other fats emphasis is often given to one particular phenomenon and 

 the real apj)earance as seen in the microscope is not reproduced. 



The only reliable representation is found in the actual photomi- 

 crograph or its exact graphic reproduction. 



When the crystals of certain fats are prepared in a special way 

 they show, with polarized light, a distinct cross, the existence of 

 which is explained by the laws of elliptical polarization already men- 

 tioned. 



This cross was first described by Messrs. Hehner and Angell in 1874, 

 in the following words : 



If some of a fat containing crystals be placed on a slide and a drop of castor oil or 

 olive oil be applied and pressed out with a thin glass cover, the depolarization of 

 light is much enhanced; a revolving black cross, not unlike that in some starch 

 gi-ains, is seen in great perfection. These crosses are most clearly defined in the 

 crystals obtained from butter, and these thus mounted form a brUMant polariscopic 

 object. 



They add further: 



Thus far, and no further, as it seems to us, can the microscope assist us in this mat- 

 ter; but even such indications are valuable, especially when subsequent analysis 

 proves the sample to be an adulterated article. The microscopic evidence in such a 

 case frequently serves to clinch together the whole superstructaire, and thus certainty 

 is made doubly sure. 



Dr. Thomas Taylor has further called attention to this phenomenon 

 in a paper road before the American Society of Microscopists at its 

 Cleveland meeting, August, 1885. On page 2 of the reprint of this 

 paper he says: 



Since the publication of that paper I have experimented largely with butter, and 

 have made the discovery that when it is boiled and cooled slowly for a period of 

 from twelve to twenty-four hours at a temperature of from 50° to 70° F., it not only 

 becomes crystallized, but with proper mounting and the use of polarized Ught it ex- 

 hibits on each crystal a well-defined figure resembhng what is known as the cross 

 of St. Andrew. In course of tirne, the period ranging from a few days to a few 

 weeks, according to the quality of the butter used and the temperature to which it 

 is exposed, the crystals, which at first are globular, degenerate, giving way to nu- 

 merous rosettelike forms peculiar to butter. 



On page 5 he says: 



About ten years ago, while making some experiments with boiled butter, I first 

 observed it exhibited small crystals somewhat stellar in form, but gave no, further 

 attention to the fact until May last. For the purpose of determining the real form 

 of the crystal of boiled butter I procured a sample of pure dairy butter from Ohio. 

 I boiled it, and when cold examined it under a power of 75 diameters. To my sur- 

 prise I found globular bodies. When I subjected them to polarized light a cross, 

 consisting of arms of equal length, was observed on each crystal. 



Prof. H. A. Weber, of Columbus, Ohio, has made some interesting 

 experiments with the microscope on fats, which, in the main, bear 

 out the conclusions of Messrs. Brown, Hehner and Angell, and Tay- 

 lor. As was to be expected, however, he has shown that the appear- 

 ance of the cross on a crystal of natural fat does not show that it was 



