120 



COLLOIDS IN BIOLOGY AND MEDICINE 



measure the amount of cloudiness so that they might determine from 

 it, the content of dissolved colloid in the fluid. 



As yet they have not been applied to biocolloids, and the relation 

 between the clouding of media in a fluid, the intensity of the light and 

 cloudiness yields a complicated curve. On this account it is still 

 impossible to determine the value of these instruments aptly termed 



by MECKLENBURG, tyndallmeters, for the 

 study of biocolloids. 



There is need of such an instrument. 

 [P. A. KOBER has devised a very satisfac- 

 tory nephelometer which has found ex- 

 tensive application in biology, especially 

 by BLOOR. See Journal of Industrial and 



FIG. 28a. Kober Nephelometer. 



Engineering Chem., Vol. VII, p. 843. Tr.] I have always felt the want 

 of being able to determine the exact content of a bacterial suspension 

 by some sort of tyndallmeter. Such an instrument must be very simple 

 to manipulate, which is not the case with the existing instruments. 



The colloid content of a solution is well measured for certain 

 purposes by 



The Fluid Interferometer. 



The fluid interferometer 1 was originally devised to determine the 

 concentration or change in concentration of crystalloid solutions. 

 According to MARC it is also available for light or yellowish colloidal 

 1 Made by Carl Zeiss, Jena. 



