SECTION VII. POLARISATION 



POLARIZED MICROSCOPY 

 IN HISTOCHEMICAL RESEARCH 



H. H. PFEIFFER 



Polarized optics, especially if applicated quantitatively, assist a micro- 

 scopist to notable contributions to our knowledge of leptonic structure 

 of biological and médical objects under physiological and pathological 

 conditions. But beyond this main tas le, researches in polarization micro- 

 scopy employed to fresh or fixed and sectioned tissues hâve also an 

 important profit for securing and relief of identification of chemical 

 compounds. Observations and measurements in polarized light are chiefly 

 situated in the foUowing directions. 



1) It occurs very rarely that definite substances may be recognized 

 only on the behaviour against polarized light, as optical négative nucleic 

 acids in contradistinction to the positive character of proteins; 



2) At some anisotropic structures there are to produce topochemical 

 reactions which are accompanied with a change of the optical character, 

 e.g. after treatment with mono-valent phenoles, sumach-extract or 

 glycerol. 



3) By Lison it has been shown that lipoids if examined with polarized 

 light can be allotted into several histochemical groups by means of 

 a thermical claim so the further analysis simplifying. 



4) The identification of crystalline précipitations comprehends trials 

 with the polarization microscope to study the occurrence of anisotropy, 

 its intensity and character, and the décision if dichroism (double 

 absorption) appears. 



5) Dichroism in ultraviolet light is found without staining in nucleic 

 acids, whose purine and pyrimidine components may be arranged in 

 parallel planes to eâch other and the electric vector of the polarized 

 light. 



6) Organic dyes such as Congo red or thionin may, in some cases, 

 be attached to tissue components in such a way that the dye molécules 

 are themselves oriented sufficiently to endow to structure with dichroic 

 properties. 



In the face of ail thèse facts we hâve to admit that the polarization 

 microscope ought to be used also in histochemistry. In some communi- 

 cations we shall become acquainted with more expériences in that 

 respect. 



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