b PROCEEDINGS OF THE ACADEMY OF 



Dr. J. Gibbons Hunt exhibited and described an improved Sec- 

 tion instrument. 



A brass tube, two inches long and three-fourths of an inch in diameter, is closed 

 at one end ; a circular brass plate two inches in diameter attached to the other 

 end, and ground properly fiat, forms the surface to guide the razor. Into this tube 

 fits another, which is worked up or down by a screw working in a thread cut in 

 the bottom of the outside tube. A slot cut through the upper end of the ovter 

 tube affords room for a lateral binding-screw, which is attached to and carried 

 by the inner tube. The binding-screw presses against a moveable tongue of 

 metal armed at the upper and inner side with minute points. On the opposite 

 side of the inner tube are also points designed to hold an object more securely. 

 The advantages of this improvement are obvious. It is cheap, and is peculiar 

 in really answering the purpose for which it is made. 



Cork is unfit for holding objects in a section instrument ; some firm vege- 

 table, such as a turnip or potato, for all very delicate preparations being far 

 better. 



Sept. 1th, 1868. 

 Director, Wm. Pepper, M. D., in the Chair. 

 Seventeen members present. 



Dr. Wm. Pepper read a paper, illustrated by microscopical prepa- 

 rations, " On the action of phosphorous in poisonous quantities upon 

 the animal economy." 



See American Journal of the Med. Sciences, April, 1869. 

 George Roberts M. D., and Ferdinand A. Hassler, M. D., were 

 chosen members of the Department. 



Sept lUt, 1868. 

 Director, W. Pepper, M. D., in the Chair. 



Twenty members present. 



A complete set of photographs of the 19 bands of Nobert's most 

 recent test plate, the last four showing spectral bands only, were 

 presented by the Surgeon General U. S. Army, through Dr. J. J. 

 Woodward. 



Dr. Leidy observed that having noticed in the recent edition of Gray's 

 Manual of Botany, the description of a species of Wolffia, for the first time 

 published as occurring in the United States, he was led to seek for it in the 

 vicinity of Philadelphia, under the impression that he had long been familiar 

 with a plant of the kind, but without knowing its true character. He was 

 successful in his search, having found it growing abundantly in a ditch skirt- 

 ing the road near the Delaware River, below the built up portion of the city. 

 It is accompanied by a profusion of Lemna polyrrhiza and L. minor. 



Dr. Leidy exhibited specimens of the plant in a glass vial and also beneath 

 the microscope. This, the smallest and simplest of all the true flowering 

 plants, appears to be the Wolffia Columbiana of Karsten, to which the United 

 States plant of other localities has been referred in Gray's Manual. The de- 

 scription in the latter is very brief, and the original is not accessible in our 

 library. The plant is larger than indicated in Gray, and may be looked upon 

 as a variety. It was described as follows : 



The frond is oval or nearly globular, uniformly bright pea-green, smooth or 

 slightly muricate, shining. Plant floating at the surface of the water, about 

 two-thirds submerged with the long diameter horizontal. No distinctive 

 appearance between the upper and lower surfaces. In a state of multiplica- 

 tion usually observed with the new frond projecting from within one end of 



