June 18, 1920] 



SCIENCE 



617 



SPECIAL ARTICLES 



AN ACCURATELY CONTROLLABLE MICRO- 

 PIPETTE 



A NUMBER of pipette devices have 'been em- 

 ployed for the injection or extraction of minute 

 quantities, which have served their purpose 

 quite satisfactorily. Among these may be 

 mentioned the several methods described by 

 Toldt,^ Barber^ and Chambers.^ However, in 

 certain recent work I was unable to use with 

 the necessary accuracy any of these methods 

 and so undertook to construct a micropipette 

 which could be very reliably and precisely con- 

 trolled. 



The simple apparatus now being used serves 

 my needs so surprisingly well that I offer this 

 description of it hopeful that the method will 



quantities of various solutions into the cyto- 

 plasm and macronucleus and have induced the 

 formation of vacuoles near the contractile 

 vacuole in sudh manner as to obtain signifi- 

 cant data on the behavior and function of the 

 latter structure. An account of these results 

 will be published in later papers; I shall here 

 only describe the method employed. I am in- 

 debted to Professor S. O. Mast for several im- 

 portant suggestions in the construction of the 

 apparatus. 



The general principle involved in the opera- 

 tion of this mechanism is the inducement at 

 will either of large or of very delicate changes 

 in a given volume of mercury by means of a 

 email steel needle attached to a finely threaded 

 thumb-screw. 



Fig. 1. It., brass tube; cg.t., capillary tube ;».6.c., "inner" brass cap; m.p., micropipette; o.i.c, 

 "outer" brass cap; r.c, rubber eylmder; r.t., rubber tube; s.d., steel disk; a.n., steel needle; t.s., 

 thumb-screw. i 



be of service to others. By its use I have suc- 

 ceeded in extracting the micronucleus from the 

 ciliate Euplotes, have injected very minute 



1 ToJdt, "Die Injection unter messbarem 

 Drucke," ArcMv. f. Mikr. Anat., 1869, 5, 167, 

 Taf. XI. 



2 Barber, M. A., "The Pipette Method in the 

 Isolation of Single Microorganisms and in the In- 

 oculation of Substances into Living Cells," The 

 Philippine Jour. Sci., Sec. B, Trop. Med., 9, 307. 



» Chambers, R., ' ' The Microvivisection Method, ' ' 

 Biol. Bull, 1918, 34, 121. 



, The mercury is contained in a capillary glass 

 tube Y <3m. in length and 6 mm. in diameter 

 with a bore of about 1 mm. Into one end of 

 the tube is sealed the micropipette (m.p.) and 

 over the other end an " inner " brass cap 

 (i.i.c), as shown in Fig. 1. 



The end of this " inner " cap is covered and 

 sealed by a thin steel disk (s.d.) having a cen- 

 tral projection which inserts a short distance 

 into an enlargement of the capillary bore. 

 .Through the center of the disk is a hole of 



