838 SUMMARY OF CURBENT RESEARCHES RELATING TO 



glass, where the preparation lies in half per cent, solution. For permanent 

 preparations picrocarmine, glycerin. 



Preparing Medullated Nerve-fibres.* — Dr. T. Boveri, when examining 

 medullated nerve-fibres, used the sciatic nerve of the frog, which was 

 treated in the following way. 



The nerve, carefully cut out from a frog recently killed, was stretched 

 out according to Eanvier's method, and placed for four hours in a half per 

 cent, solution of hyperosmic acid. It was then washed in distilled water, 

 and hardened in 90 per cent, spirit. Pieces of nerve about 6 mm. long 

 were then stained in a concentrated solution of acid fuchsin for twenty- 

 four hours, and afterwards treated for a similar time with absolute alcohol. 

 For cutting, the object was imbedded in paraffin. The author found that 

 osmic acid gave good results if the 1 or • 5 per cent, acid had come into 

 actual contact with the nerve-fibres. In practice the central fibres of a 

 bundle were only partially affected by this reagent, so that the action of 

 water preponderated over that of the osmic acid. 



For treating nerves with silver the author indicates the following 

 course : — (1) If a nerve be placed in a 1 per cent, solution of silver 

 nitrate, to which an equal volume of 10 per cent, nitric acid be added, the 

 silver reaction takes place, and the fibrillar structure of the axis cylinder 

 is to a certain extent retained, so that a periaxial space does not arise, 

 owing to shrinking of the axis cylinder. (2) Nerves freshly teased out and 

 exposed to osmic acid vapour on a slide in a half dry state are treated with 

 a dilute watery or alcoholic silver solution. In well-hardened fibres the 

 silver reaction occurs almost at once. 



It may be remarked here that a mixture of equal volumes of 1 per cent, 

 silver solution and 1 per cent, osmic acid gives the same reaction on fresh 

 tissues as the silver solution shows by itself; hence this mixture is 

 especially suitable for demonstrating the boundary parts of cells, and also 

 for preserving the elements at the same time. 



Demonstrating Sharpey's Fibres.! — ^^- ^- Kolliker had only poor 

 results when examining Sharpey's fibres in thin sections of decalcified bones 

 of adults in water or dilute spirit. Far superior were 5-10 per cent, 

 salt solution, acetic acid of various strengths, oxalic acid, and strong hydro- 

 chloric acid. Of the stains the most satisfactory was indigo-carmine, by 

 which Sharpey's fibres were stained red, the rest of the bone-tissue blue. 

 A section of the bone cartilage, rendered transparent with concentrated 

 acetic acid, is placed for a quarter to one minute in the undiluted stain ; 

 then, after having been carefully washed, mounted in glycerin or balsam. 

 Lithia-carmine and, less so, safranin, stain the fibres and the rest of the 

 bone substance differently. New solid green 3 B, tartrazin Victoria blue B, 

 Victoria blue 4 E, auramiu, htematoxylin, osmic acid, palladium chloride, 

 picric acid, and fuchsin were without effect. 



With the polariscope and crossed nicols Sharpey's fibres appear dark 

 transversely and bright longitudinally ; for this accurate vertical focusing 

 is necessary. Elastic fibres, rendered evident by acetic acid, are dark 

 longitudinally. They are to be distinguished from Sharpey's fibres by 

 treating sections with acetic acid, oxalic acid, and hydrochloric acid, or by 

 destroying them with strong cold caustic potash or soda, or by staining 

 (the elastic fibres) with fuchsin or safranin. 



In preparations obtained by grinding bone Sharpey's tubules contain air, 

 and after the addition of turpentine oil and balsam stand out quite clearly 



* Abh. K. Bayer. Akad. Wiss., xv. pp. 423-94 (2 pis.)- 

 t Zeitschr. f. Wiss. Zool., xliv. (1886) pp. 644-80 (4 pis.). 



