312 SUMMARY OF CURRENT RESEARCHES RELATING TO 



disposed with much regularity all round t.lio nucleus. As they increase 

 in sizo they almost touch, and in consequence the protoplasm proper is 

 reduced to a delicate framework. 



The procedure for showing the structural peculiarities of the inter- 

 stitial colls consists in fixing the pieces in the chrom-accto-osmic acid 

 mixture, and staining the sections after Flemming's method with safranin. 

 After dehydration the sections are placed in oil of turpentine. By this 

 means tho glohulcs blackened by the osmic acid aro for the most part 

 dissolved; in those that remain the intensity of colour is much 

 diminished. Sometimes the cell assumes a more or less deep lilac 

 tint. 



Methods of investigating Structure of Nerve-tissues.*— Mr. F. 

 Nansen, in his studies on the structure of nervous tissues, made use of 

 fresh isolated tissues, as well as of those that had been macerated or cut 

 into sections. The first were examined in the blood of the animal from 

 which they were taken, either as large pieces or after being teased with 

 glass-needles, the use of which the author strongly recommends. For 

 macerations use was made of B. Haller's fluid composed of 5 parts 

 acetic acid, 5 parts glycerin, and 20 parts distilled water ; pieces were 

 treated with this for from one to twenty-four hours, then teased in 

 50 per cent, glycerin, or washed and stained with ammonia-carmine or 

 picro-carmine. Delafield's solution is specially recommended. For 

 some purposes it was better to macerate in dilute alcohol, when weak 

 solutions (17-20 per cent.) were found good. Sometimes, however, this 

 process has to be continued for weeks ; when finished, the tissues were 

 stained in ammonia-carmine diluted with an equal quantity of macera- 

 ting fluid for twenty-four hours, and teased in glycerin of 50 per cent. 



The author usually stains before teasing or isolating, because he 

 thinks it much more practical, and when one is careful not to employ 

 too strong solutions, and to dissolve or dilute the staining colours in 

 the macerating fluid, the facility of isolation is not seriously disturbed. 

 Though one of the oldest methods, that of maceration in potassium 

 bichromate is one of the best, and must never be omitted when it is 

 wished to examine the most delicate structure with good results. 



The most important thing in researches on the histology of the 

 nervous elements is to get good sections from well fixed and stained 

 preparations. The author strongly recommends Flemming's mixture as 

 made of 15 parts of 1 per cent, chromic acid, 4 parts of 2 per cent, osmic 

 acid, and 1 part (or less) of acetic acid. Pieces as small as possible 

 must be treated in not too small quantities of the fluid for from 12-24 

 hours, or even longer. After washing they should be directly inclosed 

 (not imbedded) in paraffin, and may then be easily cut under alcohol or 

 water. Mr. Nansen has succeeded in getting sections only ■ 005 mm. 

 thick. 



A method which was found very useful with Mollusca was the fol- 

 lowing : — The pieces for examination, cut as small as possible, were 

 treated with 1 per cent, osmic acid for 48 hours, then washed in running 

 water and cut at once by hand, or with the microtome (or they may bo 

 first hardened in alcohol and then cut). The sections were stained in 

 Delafield's hamiatoxylin (diluted), and the colour destroyed in water 

 containing a little acetic acid ; the sections were examined in glycerin 



* Bergens Museum Aarsberetning for 1S86 (18S7) pp. 73-80. 



