BIOLOGICAL AND MICROSCOPICAL DEPARTMENT. 5 



in a spiral direction analogous to dentinal tubuli in secondary 

 dentine. 



Dr. F. W. Lewis inquired what diflference there was between 

 these exostoses and epulis. 



Dr. James Tyson remarked that, microscopically, true epulis 

 is a fibrous tissue, and springs from the mucous membrane, 

 although the giant-celled myeloid tumor (giant-celled sarcoma of 

 Yirchow) generally springs from bone, and is sometimes incor- 

 rectly called epulis. With regard to the nature of cementum, Dr. 

 T. suggested that it seemed more philosophical to place it in the 

 same category with bone, since it only differed from true osseous 

 tissue in the absence of Haversian canals for minute bloodvessels, 

 which were unnecessary on account of the close contiguity of 

 the structure (cementum) to its vascular supply. 



Dr. Tyson also showed an ingenious gastric canula, improved 

 b}' himself by the addition of a cover and catch for preventing 

 the loss of gastric juice, an accident which is constantly occurring 

 with the ordinary cauula in consequence of the animal's scratch- 

 ing out the cork after the instrument is adjusted in the fistula 

 from the stomach. 



• 



February 20. 

 conversational meeting. 

 Seven members present. 



March 6. 

 Director S. W. Mitchell, M.D., in the chair. 

 Eight members present. 



The Corresponding Secretary presented photographs of the test 

 Diatoms Surirella gemma and Amphi2)leura pellucida (the latter 

 exhibiting 91,000 strias to the inch) from Col. J. J. Woodward, of 

 the Army Medical Museum at Washington, and moved a vote of 

 thanks for the same, which was carried unanimously. 



Dr. J. H. McQuillen exhibited half a dozen microscopical slides, 

 handed to him by Dr. R. W. Yarney, of New York, viz. : Trans- 

 verse section of the maxilla of a cat, with the incisors, canines, 

 and molar teeth in position ; nodules of secondary dentine ; sec- 



