306 



Addis 



The 'last 4^ feet of the tubing are coiled spirally within a tank of 

 water (V), and the lower end emerges through the side of the tank at the 

 level of the stage of a microscope and terminates in a stop-cock (fig. 1). 



The next part of the apparatus is an adaptation of Bogg's modification 

 of Brodie and Russell's method (2). Bogg's apparatus consists of a small 

 circular metal box, the floor of which is of glass. The box is closed above 

 by an inverted truncated glass cone. It is pierced on one side by a small 

 metal tube which ends in a nozzle (figs. 1 and 2). 



The metal tube is screwed on to the stop-cock on the side of the tank. 



Fig. 1. — Diagram showing the stage apparatus in section. 



V, tank of water; P, flexible metal tabing ; (, metal tube acrewing into tap; e. troncated glass cone in 

 positioD ; M, low-power lens of microscope ; R, box hang below the stage to catch the oil which flows 

 oat of UiS coi^E^alometer. 



The box is then fitted on to it and locked by a small brass collar which fits 

 into pegs driven into the tube and the side of the box, so that any rotation 

 of the tube in its socket is rendered impossible. A special nozzle must be 

 fitted on to the end of the tube. It is made of soft brass, and is about half 

 a millimetre in diameter and 4 ram. long. It is essential that the nozzle 

 should point in exactly the right direction. It should be placed so that 

 when the stop-cock is turned and a jet of oil issues from it, the stream 

 travels tangentially against the edge of the drop of blood which hangs 

 from the end of the glass cone. This direction has to be determined ex- 

 perimentally by making slight alterations in the direction of the tube with 



