524 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Owing to the thick stratum of fluid traversed by the light, the 

 absorption-bands appear, even with a solution only containing 

 1/100,000 of haemoglobin. A drop of blood the size of a grain of 

 wheat, on a piece of linen exposed three months in the open air, 

 showed very distinctly after maceration in fluid enough to fill the 

 5 dm. tube the absorption-bands of haemoglobin, and the author has 

 found the absorption-bands still perfectly visible in a fluid which 

 under ordinary circumstances presented no colour, and which only 

 contained 1 com. of blood in 30 lit. of water. With urine the results 

 are almost as satisfactory. 



The tubes being entirely of glass, the fluids can be submitted to 

 the chemical actions which allow the oxyhsemoglobin to be reduced, 

 and its presence verified by the appearance of the characteristic black 

 band. 



This apparatus can of course be used in all cases where the 

 process of spectroscopy by absorption admits of application, as in the 

 determination of the presence of chlorophyll. The author has, more- 

 over, applied it to the detection of very small quantities of ergot in 

 wheat-flour, by means of the distinctive absorption-spectrum which 

 the colouring matter of ergot presents. 



Apparatus for Microscopical Observation of Vapour-drops.* — 

 Prof. J. L. Soret describes an apparatus by which drops of vapour 



Fig. 107. 



can be examined microscopically. It depends upon the principle that 

 when moist air is rarefied by an air-pump a precipitation of vesicular 



* Arch. Sci. Phys. et Nat., xiv. (1885) pp. 575-6. 



