STAINING, PRACTICAL AND THEORETICAL 



Notes: 



{a) The time required for hydrolysis by the enzyme (pepsin or 

 papain) will depend upon the size and thickness of the sections 

 or tissue blocks and their connective tissue characteristics. In 

 those tissues where connective tissue is abundant, the time must 

 be prolonged. However, care should be taken to avoid over- 

 hydrolysis and consequent disintegration of the remaining tissue. 



{h) The author (Bernick) observes that the dermis of the skin 

 is composed of collagenous elements, of varying thickness, 

 which interlace each other to form a network, and that these 

 collagenous fibres are irregularly arranged and may become 

 blackened with silver if such a section has not been pretreated 

 with enzymes, as above. 



{c) It is stressed that the enzymatic protein-hydrolysis des- 

 cribed above does not remove the collagenous fibres completely. 

 The action depends upon the density of the fibres present. The 

 periodontal membrane, for example, contains a heavy concentra- 

 tion of collagenous elements and with enzymatic hydrolysis only 

 partial loss of fibres results, but even this incomplete removal, the 

 author states, permits the clear and accurate identification of 

 the nerve supply to the membrane. 



[d] For more detailed information the original paper should be 

 consulted. 



Reference: Bernick, S. (iQSS). 



SILVER NITRATE - GOLD CHLORIDE 



For demonstrating layers in human neurological lipofuscin 



granules 



(After Nassar, Issidorides & Shanklin, i960) 



Solutions required: 



A. Potassium permanganate, 5% 



aqueous 



B. Sulphuric acid, 5% aqueous 



C. Solution A . . . . • • 25 ml. 

 Solution B . . . . • . 25 ml. 

 Distilled water . . . . . . 450 ml. 



D. Oxalic acid, 2% aqueous 



414 



