132 



Mr. H. Hartridge. Factors Affecting the [Nov. 1, 



Experimental Demonstration of the Factors that Control the Position of 

 Boundaries and Mean Wave-lengths of Absorption Bands. 



Theoretical considerations showed that the factors of importance are : — 



(1) The number of molecules of pigment encountered by light in trans- 

 mission {i.e. concentration x thickness). 



(2) The initial intensity of incident light. 



(3) The activity of the retinal response. 



(1) The effects of alterations in concentration or thickness of the solution 

 under examination are well known, having been first investigated by 

 Rollett.* These observations have been repeated with the new method, the 

 results being given in the table below and shown graphically in fig. 2. 



The widths of the bands increase with an increase in concentration or 

 thickness of the solution till a point is reached when fusion of the neigh- 

 bouring bands takes place. The mean wave-lengths of the a- and /3-bands, 

 on the other hand, do not appeax to be affected by changes in concentration, 

 and this would point to the bands being symmetrical in form. Mention^has 



Table III. — Effect of Change in Concentration on Mean Wave-length and 



Boundaries of 2 Hb Bands. 



Hb. 





B. 



C. 



D. 



E. 



F. 



a. 



H. 



I. 



J. 



per cent. 























0-1 



7260 





5764 









5403 







4210 



2 



7260 



5800 



5765 



5738 



5600 



5485 



5401 



5345 





4420 



3 





5810 



5765 



5733 



5600 



5487 



5403 



5340 





4590 



0-4 





5829 



5765 



5716 



5602 



5490 



5400 



5310 





4690 



0-5 





5837 



5762 



5703 



5604 



5505 



5397 



5300 





4750 



6 





5843 



5765 



5685 



5607 



5526 



5396 



5290 





4830 



0-7 





5856 



5759 



5678 



5608 



5540 



5395 



5265 





4880 



0-8 



7210 



5860 





5678 



5612 



5546 





5250 





4950 



0-9 



7160 



5865 







5610 







5230 



5130 



5000 



1 



7130 



5863 













5226 



5126 



5010 



1 1 





5864 













5210 



5123 



5010 



1 2 





5876 













5180 



5123 



5030 



1 3 





5880 















5125 





1 '4 





5886 



















2 



7000 



5900 



















A, the apparent commencement of spectra in the infra-red. 



B, the yellow edge ; D, the green edge ; C, the mean wave-length of the a-bands. 



E, the centre of unabsorbed area between o- and /3-bands. 



F, green edge ; H, blue edge ; and Gr, mean wave-length of /3-band. 

 I, centre of unabsorbed area between f}- and 7-band. 



J, green edge of 7-band. 



* Schafer, ' Text-Book of Physio].,' vol. 1, p. 233. 



