Section 1: MORPHOLOGY AND ANATOMY 



OF THE DEVELOPMENT OF INSECTS 



SOME HISTOLOGICAL STUDIES ON INSECT GROWTH 



Некоторые гистологические исследования по развитию насекомых 



V. В. WIGQLESWORTH 



(Department of Zoology, University of Cambridge, England) 



During the past few years the use of osmium textroxide followed by ethyl 

 gallate has been developed as a method of fixation and staining (Wiggles - 

 worth, 1957b). The purpose of this communication is to describe this method 

 and some of the results which have been obtained with it, particularly on 

 growing tissues. 



It has long been recognized that osmium tetroxide is the best of all cytologi- 

 cal fixatives. With the development of electron microscopy its properties 

 have been appreciated even more highly. Moreover it is claimed that a large 

 part of the image of the cell as seen with the electron microscope depends 

 on the scattering of electrons by localized deposits of bound osmium. If, there- 

 fore, this osmium could be made visible in the light microscope we should 

 expect to obtain an image similar to that seen twith the electron microscope. 



The nature of fixation by osmium tetroxide is not known. It may be that 

 more than one oxidative change in the components of the cell is involved. 

 But it is quite certain that one important effect is the fixation of lipids. A very 

 large part of the lipids in the cell, which are located in the mitochondria, 

 endoplasmic reticulum, Golgi bodies, cell membrane and nuclear membrane, 

 is in the form of monomolecular layers of oriented fatty chains. These chains 

 are made up of unsaturated fatty acids; and since the fatty acids concerned 

 have a constant composition, the unsaturated bonds will lie adjacent to one 

 another in the oriented films. It is suggested that an important element in fix- 

 ation by osmium tetroxide is cross-linking or polymerization of these fatty 

 chains. 



There are many ways in which such cross-linking could take place. One 

 of the possibilities is indicated in fig. 1. The osmium bound in the manner 

 shoA\ni is still callable of further oxidative reactions. It would still react with 



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