138 THE AMERICAN MONTHLY [Jnne, 



above stated the appearance is usually that of a dark net-work on a light 

 field, though with some observers both may be seen, or possibly the 

 latter may be the more prominent. 



Such, in brief, seems to be the explanation of the manifestation of this 

 vascular net-work. 



There are other methods of rendering this apparent, but as they do 

 not involve the use of a microscope, they need not here be mentioned. 



This experiment has always seemed to the writer to be an exceed- 

 ingly interesting one. Nothing could be simpler, yet it enables us to 

 gain a glimpse of the minute structure of our own retina, a feat we 

 should be inclined to believe exceedingly difficult. 



MEDICAL MICROSCOPY. 



By Dr. F. BLANCHARD, 



WASHINGTON, D. C. 



Artificial Cultivation of Ringworm Fungus. — Dr. H. L. Rob- 

 erts, in the British Journal of Dermatology^ 18S9, p. 359, records 

 his observations upon Trichophyton tonsurans under cultivation. 

 The culture medium used was saccharine infusion of malt and alkalin- 

 ized beef-broth incubated at 30° C. 



The fungus began its development in 24 hours, and in three or four 

 days from the formation of the primary colony secondary deposits were 

 visible. If the colonies rose to the surface, they speedily became cov- 

 ered with a white powder. On microscopical examination the my- 

 celium was found to be regularly septate and filled with a granular 

 protoplasm. When development takes place in air, the mycelium be- 

 comes finer, the segments are small, and the terminal fruit-bearing 

 filament may end in an ampulla. The spores are pear-shaped, are at- 

 tached by their narrow end, and are sometimes seen to project from the 

 ampullaj. 



Inoculation experiments on guinea pigs, and on the author's own 

 arm. gave the usual characteristics of ringworm. 



The author concludes that Trichophyton is " a fungus able to vary 

 its form and activity according to the physical and chemical proper- 

 ties of the soil on which it grows." Asa saccharine medium has been 

 found to be the most favorable soil, it follows that the animal skin is 

 unsuitable; hence, " the ringworm fungus vegetates, but does not de- 

 velop " there. 



Pathology of Chorea. — Dr. E. D. Fisher recently read a paper 

 before the New York Neurological Society upon this obscure subject. 

 Among the lesions noted were a temporary increase of connective tis- 

 sue in the brain in rheumatic cases, blood extravasations, embolism, 

 thrombasis, and dilatation of the smaller vessels. 



In chronic chorea these conditions have caused degeneration and a 

 fine general sclerosis of the brain. 



Transformation of Microbes. — M. A. Chauveau has continued 

 his researches on the limits, conditions, and consequences of the varia- 

 bility of Bacillus anthracis. He finds that this bacillus may exhibit 

 three types, the respective properties of which appear to have been 

 definitely acquired. 



