618 



SCIENCE 



[N. S. Vol. LI. No. 1329 



size just convenient to accommodate the en- 

 trance of the steel needle into the capillary 

 tuhe. The needle, 3 cm. long and about 2/5 

 mm. in diameter, is soldered on to a finely- 

 threaded thumb-screw (t.s.) which operates in 

 a brass tube (h.t.). This tube is screwed 

 firmly into the base of an "outer" brass cap 

 (o.h.c). In the inner end of the brass tube, 

 the needle passes through a hole having a diam- 

 eter the same as that in the steel disk. Into 

 the " outer " cap is fit very closely a soft rubber 

 cylinder (r.c), in length one half that of the 

 cap, through the center of which passes the 

 needle. Inserting the needle into the hole in 

 the steel disk, the " outer " cap is now screwed 

 tightly on to the " inner " cap. 

 , The device is supported and adjusted on the 

 microscope stage by means of the Barber 

 pipette-holder. 



After the capillary tube and pipette are 

 fiUed from a column of mercury contained in 

 the rubber tubing (ri.), the system is then 

 closed by the stopcock and is ready for opera- 

 tion. This is accomplished by regulating the 

 thumb-screw which is threaded 60 turns to the 

 inch. Yery slight movements of it induce 

 gradual changes of the meniscus of mercury in 

 either direction in the tip of the micropipette 

 (having a lumen of about five microns) ; these 

 changes may be so delicate as to be almost in- 

 perceptible under a magnification of 400 

 diameters. 



, Two precautions are here worthy of note, 

 viz., the use of glass tubing and mercury which 

 are thoroughly clean, and the avoidance of air- 

 bubbles anywhere within the system. To clean 

 glass tubing, I have found the following 

 method very effective: after sealing one end of 

 the tube, put into it a few drops of 95 per 

 cent, alcohol and a like amount of concentrated 

 HNOj. Upon adding a drop or two of BLSO^ 

 an explosive reaction occurs -Which apparently 

 oxidizes thoroughly any substances adhering 

 to the surface of the glass. (The tube, of 

 course, should be turned away from one's face 

 before adding the II,SO^.) Break off the sealed 

 end and wash the tubing well with distilled 

 water. 



To hasrten the filling of the system with mer- 



cury and to remove air that may appear, it is 

 advisable to fill nearly fuU the capillary tube 

 (and add a drop of dust-free, distilled water 

 which can be forced through the pipette point 

 more easily than mercury) just before sealing 

 in the pipette. 



It is advantageous, also, to have the shank 

 of the pipette fit fairly well the bore of the 

 tube; air-bubbles are then less likely to appear 

 in the sealing-wax between the shank and the 

 surface of the bore. 



The needle-pipette operates inside a moist 

 chamber similar in design to that described by 

 Chambers (loc. cit.). Distilled water or solu- 

 tions of any sort for injection purposes may be 

 drawn into the pipette after the mercury has 

 been forced to the tip by turning the thumb- 

 screw, then dipping the tip into a hanging 

 drop of the solution and drawing a desired 

 quantity of this into the pipette by reversing 

 the movement of the screw. Obviously, clean- 

 sing with distilled water, which is sometimes 

 essential, may be done in a similar way. 



To extract cytoplasm or to remove a nu- 

 cleus, a small amount of distilled water is 

 drawn into the pipette, the tip then inserted 

 into the organism and the operation completed 

 by carefully manipulating the thumb-screw. 

 0. V. Taylor 



The Johns Hopkins UNiVERSirT 



THE AMERICAN PHILOSOPHICAL SO- 

 CIETY. Ill 



SATURDAT, APRIL 24 



Executive Session — 9:30 o'clock 

 Stated Business. — Candidates for membership 

 ballotted for. Appropriations for the ensuing year 

 passed. Annual address of the president. 



Morning Session — 10 o 'clocTc 

 George Ellert Hale, Ph.D., Sc.D., LL.D., vice- 

 president, in the chair 



The problem of fhe evolution of the solar sys- 

 stem: Ernest "W. Brown, Sc.D., professor of 

 mathematics, Yale tTniversity. 



Certain aspects of recent spectroscopic observa- 

 tions of the gaseous nebulce which appear to estab- 

 lish the relationship between them and the stars: 

 W. H. Wright, astronomer, Lick Observatory. 



