Hdckel vs. Virchow. 295 



the oil globules. To detect and remove the mycelium of any 

 fungus that may be present, add to the specimen of butter a 

 solution composed of equal parts of turpentine and alcohol, shake 

 well and allow the mixture to stand several hours in a tall vessel. 

 The salt will fall to the bottom, the curd will follow, carrying 

 with it the mycelium, and the oil will appear on top, combined 

 with the turpentine. Decant the clear oil and dissolve the curd in 

 acetic acid. If any mycelium was present it will remain after the 

 curd is thus dissolved, and can be examined under the microscope 

 in the usual manner. 



In Plate XXL, I have endeavored to indicate the microscopical 

 appearances of oleomargarine and butter described above. Fig. i 

 represents pure butter ; Fig. 2 the same slightly heated ; Fig. 3 

 boiled olein, the oily constituent of butter ; Fig. 4 the solid por- 

 tion of boiled butter ; Fig. 5 oleomargarine ; Fig. 6 olein of boiled 

 oleomargarine ; Fig. 7 the solid fats of boiled oleomargarine ; 

 Fig. 8 fungi found in rancid butter. 



Department of Agriculture, 

 Washington, D. C. 



[Well-made oleomargarine may be quite free from any crystal- 

 line appearance, at least while fresh. We have examined a num- 

 ber of specimens from different sources with this result. The 

 sudden cooling with ice in the manufacture seems to prevent the 

 immediate formation of crystals, but it is not unlikely that these 

 will gradually form in course of time. 



In its natural condition, and before it has been subjected to 

 fusion, very careful scrutiny with the microscope is required to 

 distinguish oleomargarine from real butter. Ed.] 



HACKEL vs. VIRCHOW. 



BY WALTER C. HUBBARD. ^ 



To the microscope, as an instrument of research, we are in- 

 debted for many of the remarkable advances in biology, which the 

 morphological studies of Hackel have given to modern science. 



Considering the attention given to Hackel's theories, fostered by 

 the recent publication of his work on the development of man, a 

 reference to his " Free Science and Free Teaching," lately pub- 

 lished with a preface by Prof. Huxley, may be of interest. This 



