254 PRACTICAL MICROSCOPY. 



of ammonio-sulphate of copper, already alluded to as 

 being used for purposes of photomicrography, and the 

 figure here shows us how completely the red end of the 

 spectrum is cut off, and how little of the actinic portion is 

 absorbed. C is given to show how mixtures of substances 

 may be detected ; the illustration represents the absorption 

 bands of Parisite a brown and somewhat rare mineral 

 from the emerald mines of New Granada. It consists 

 principally of the carbonates of cerium, lanthanium, and 

 didymium, the spectrum of the last showing out with its 

 usual distinctness. At D may be seen the spectrum pro- 

 duced by a colouring matter obtained from the wing 

 feathers of the Cape lory (Turacus albocristatus) by Pro- 

 fessor Church, and to which he has given the name 

 "turacine." E shows the spectrum (or one of them) of 

 chlorophyll, and is characterised by the deep broad band 

 in the red end of the spectrum ; K, the orange colouring 

 matter obtained from aphides by Mr. Sorby, remarkable 

 on account of the band in the yellow. F, G, H, and I form 

 a series ; they are the spectra of blood and its modifications. 

 F is fresh blood ; G deoxidised blood ; H blood treated 

 with citric acid ; while I is similar to H but deoxidised. 



Mr. Sorby published an important paper on this subject 

 in vol. vi. of the * Monthly Microscopical Journal/ Fresh 

 blood gives two dark bands in the green part of the 

 spectrum, as is shown at F. This colouring matter is 

 haemoglobin, and the series of changes produced by several 

 reagents may be observed there. A small quantity of 

 fresh blood diluted with a little water should be inserted 

 in the tube shown in Fig. 218, and, examined upon the 

 stage of the microscope, the two bands in the green will be 

 plainly perceived. Next add a trace of ammonia, a small 

 quantity of Rochelle salt (double tartrate of potash and 

 soda), and a particle of the protosulphate of iron and 



