By F. VANDERPOEL, of Newark, New Jersey.
VANDERPOEL'S SETTLING TUBES.
In the February number of this Journal the writer described a new settling tube for urinary deposits which possessed several advantages over the old method with conical test-glass and pipette. For several reasons, however, the article was not illustrated, and it is for the purpose of elucidation by means of illustration, as well as to bring before the readers of the Journal two new and improved forms of the tube, that space in these columns is again sought. The first two of the figures, 1 and 2, represent the tube as originally devised; 1 denoting the tube with movable cap secured to it by means of a rubber band, and 2 the tube with a ground glass cap and stop cock. The first departure from these forms is shown at 3, and consists of a conical tube, as before, but provided with a perforated stopper, the side opening in which communicates with a side tube. The perforation in the stopper, which is easily made by a glass blower, thus allows the overflow, when the stopper is inserted into the full tube, to pass into the side tube. The stopper is then turned so as to cut off the urine in the latter from that in the large tube, and the latter is thus made tight. After allowing it to remain at rest long enough to permit subsidence of all that will settle, the stopper is gently turned and a drop taken off the lower end upon a slide, to be examined at leisure with the microscope.
The cap, ground and fitted upon the lower end, is put there as a precautionary measure, as will be seen farther on.
The tube shown at 4 is, we think, an improvement upon all of the foregoing, for upon it there is no side tube to break off, and everything is comprised in a small space. As will be seen by referring to the figure, there is a slight enlargement in the ground portion of the stopper end of the tube, this protuberance coming down about one-half the length of the stopper, which is solid and ground to fit perfectly. The lower half, however, is provided with a small longitudinal slit or groove, the lower end of which communicates with the interior of the tube, while the upper end just reaches the enlargement in the side of the latter. Thus in one position of the stopper there is a communication between the tube and the outer air, while in all other positions the tube is quite shut. In all these tubes care must be taken to fill them completely with the urine, and to allow no bubbles of air to remain therein.
The first of these settling tubes was made without the ground cap on the lower end, the latter being inserted into a small test tube for safety. At the suggestion of Mr. J.L. Smith the test tube was made a part of the apparatus by fitting it (by grinding) upon the conical end, and in its present form it serves to protect the latter from dust and to prevent evaporation of the urine (or other liquid), and consequent deposition of salts, if, for any reason, the user should allow the tube to remain suspended for several days.
These tubes will be found very useful for collecting and concentrating into a small bulk the sediment contained in any liquid, whether it be composed of urinary deposits, diatoms in process of being cleaned, or any thing of like nature; and, as the parts are all of glass, the strongest acids may be used, excepting, of course, hydrofluoric acid, without harm to the tubes. - American Microscopical Journal.
[Continued from SUPPLEMENT, No. 594, page 9491.]