Figure 1 . Drabkin and Austin cuvette . 

 The drawing is a vertical section 

 through the centre of the cuvette and 

 is to scale, except the chamber C 

 whose actual depth is only 0-007 cm ; 

 E, entry and exit capillary tubes. The 

 broken arrow indicates the direction 

 of passage of radiant flux ; the 

 direction is horizontal when in position 

 for reading in the spectrophotometer. 

 The photograph is of the unassembled 

 cuvette, lying on its side. 



SHIEL DED 

 LIGHT SOURCE 



Figure 2. Arrangement for continuous direct spectrophotometrie 

 observation of circulating blood in vivo 10 . The alignment of the 

 polarization spectrophotometer assembly {Bauseh & Lomb), perma- 

 nently set up in a dark room, is shown. The observer, reading through 

 the eyepiece E. P. of the spectrometer, is completely shielded from 

 the light L as the lamp housing L. H. and the accessory biprisms 

 which split the light into two parallel, optical paths are enclosed in 

 an additional large box shielding. Insert 1 — a rectangular mono- 

 chromatic L' photometric field of two halves P. F. of 20 A in width 

 is defined by a diaphragm in E. P. Different wave-lengths are 

 brought into position by rotation of a drum W. D. translated into 

 rotation of the prism housed within P. H. from red r to blue b or 

 vice versa, about the pivotal point P. The photometer scale P. S., 

 after matching the half fields, is read at R. Insert 2 illustrates the 

 introduction of the 0*007 cm depth cuvette into the femoral artery 

 F. A. The arrangement of clamps is shown. The passage of blood 

 through the cuvette C. may be arrested and the circulation by-passed 

 by closing the clamps at the entry and exit capillaries of the cuvette 

 and opening the clamp 8. P. in the by-passing channel. The connections 

 at the clamp sites between the glass capillaries are of small bore, 

 pure gum tubing. 



