128 



metei-') of Dr. W. J. H. Moll, which enables iis (o measure (he 

 turbidity from moment to moment. 



The principle of (liis apparatus may be discussed in a few words: 



A powerful light-source is firmly set up between two surface 

 thermobatteries I and II, after Molt-. They aie both connected to 

 a mirror-galvanometer, thus counteracting each other. Between the 

 lamp and the thermobattery I is placed a cuvette filled with water; 

 between the lamp and the thermo-battery II a cuvette filled with 

 the blood-plasm. 



Consequently the light that is directed on to the thermo-batteries 

 is weakened on the one side by water, and on the other by blood- 

 plasm. Through displacement of one of the thermo-batteries or through 

 changing the position of the lamp the unevenly weakened light may 

 be njade to fall upon the thermo-batteries with equal force. The 

 two thei-mo-electi'ic currents thus elicited, will then be equal, the 

 galvanometer will receive a current 0, the image reflected by the 

 mirror will occupy the 0-position. The apparatus has then been 

 "adjusted". The slightest change in the turbidity of the plasm 

 disturbs the equilibrium and yields a deflection of the galvanometer ; 

 the apparatus acts so quickly that after a contingent sudden change 

 in the turbidity the reflected image will come to rest again within 

 a few seconds. Moreover a procentic measurement may be taken 

 of the changed turbidity with the aid of a so-called compensation- 

 switch. 



Now our procedure is as follows: Into a sterile, dry Record- 

 syringe of 10 c.c. with a sharp, dry needle, 1 c.c. of a clear sterile 

 solution of 1 7j potassium oxalate in 0.85 "/^ common salt is sucked 

 up; the needle is inserted into a cubital vein and the blood is 

 aspirated to 10 c.c. Due regard should be given to an easy flow 

 of the blood into the syringe, so that no air is drawn in along 

 with it. The mixture thus obtained, is centrifugalized during 20 

 minutes in sterile centrifugation-tubes, which causes the blood- 

 corpuscles and the blood-platelets to precipitate and the supernatant, 

 more or less turbid plasm can be pipetted off and transmitted to 

 sterile tubes. Three c.c. of this oxalate-plasm (measured very care- 

 fully with sterile pipettes) are put into pure, and dry cuvettes. The 

 cuvettes used by me are made of the same glass and have precisely 

 the same dimensions, so that not only the thickness of the fluid- 

 layer, but also the level to which the cuvette is filled, is always 

 the same in every one of them ; in other words the contact-plane 



1) Dr. W. J. H. Moll, Een extinctiemeter. Verslag Koninklijke Akademie van 

 Wetenschappen, Wis- en Naluurkimdige Afdeeling, 27 Maart 1920. Deel XXVlIl. 



