CYTOCHEMICAL TESTS ON EMBRYOS 



5i^l 



3. Tryptophane : Tryptophane compriaes from 1 to 5^ of the great majority of 



proteins. Its formula follows: 

 H • 



- C - C^ — CH(N^) - COOH 



H H 



Fig. 8. Testis of Rana ridibunda perezi. Arginine reaction (green filter). 



Fig. 9. Spermatozoa of Helix aspersa, heads to upper left. Arginine reaction. 



Fig. 10. Salivary gland chromosomes of Chlronoraus larvae. Tyrosine reaction. 



Fig, il. Salivary gland chromosomes of Chironomus larvae. Tryptophane reaction. 



Photographs by courtesy of J. A. Serra 



Since this amino acid results from the hydrolysis of many proteins and 

 the test is sensitive, a satisfactory procedure is available for animal tis- 

 sues. 



a. Harden the tissues in 10^ formaldehyde, if they were not previously 

 fixed In a formalin fixative, for 5 hours; wash well. 



b. Immerse for 5 to 5 seconds in an aqueous solution of sodium silicate. 



c. Immediately Immerse the pieces In Volsenet reagent for 10 to 15 

 minutes, in a small glass-stoppered bottle. This reagent is made by 

 adding 1 drop of 2% aqueous formol and 1 drop of 0.15^ aqueous NaNC^, 

 with stirring, to 10 cc. of concentrated HCl. Solution is freshly 

 made before using. 



d. Mount in glycerine and observe directly. Tissues may be compressed 

 apart between coversllp and slide. The color fades hence the tissue 

 must be examined within a few hours. 



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