526 SUMMARY OF CUEEBNT RESEARCHES RELATING TO 



Flemming's fluid, Hermann's fluid, picro-sulphuric, picro-acetic and 

 picric acid saturated in 50 p.c. alcohol, but of these the Flemming and 

 Hermann preparations yielded the best results. For the smaller larvae 

 it was not necessary to dissect before fixation, but for older lavse and 

 pupas the head was removed to make penetration easier. For adult 

 material, where penetration is difficult, the best fixative was acetic acid, 

 generally a 10 or 20 p.c. acetic solution in 80-100 p.c. alcohol. 

 Kleinenberg's picro-sulphuric and picric acid in 50 p.c. alcohol were also 

 used, with fair results when the head was cut in two. 



The material was all cut in paraffin, and it was found that for adult 

 material long imbedding was necessary, 4-8 hours, to get the paraffin all 

 through the tissues. Some material was imbedded for a shorter time to 

 see whether the heat had produced any artefacts in the other material 

 which was imbedded for the longer period, but in such cases the lens 

 invariably separated from the retinular layer, no difference was observed 

 in the internal tissues due to long heating. In staining, the best results 

 were obtained in the use of Heidenhain's iron-haematoxylin, and 

 by a strong mordant for a long time. For material of this kind 

 there seems to be no better stain. It was found that by destaining to 

 different degrees the various parts of the eye would show differences in 

 colour, the rhabdome, for example, staining an intense black in rather 

 deeply stained material. The nerve fibrils of the retinular cells also 

 stained black with this stain. Other stains, such as Delafield's 

 hfematoxylin and eosin or Bordeaux red, were employed with very good 

 results. 



For depigmenting, Grenacher's solution with a somewhat greater 

 percentage of acid was used. Parker's solution was also used, though the 

 former gave better results. 



Imbedding with Incomplete Dehydration.* — W. J. V. Osterhout 

 gives the preference to a saponaceous medium for imbedding vegetable 

 tissues over paraffin. He finds that cocoanut oil and sodium hydrate 

 when mixed in the proportion of 70 c.cm. of oil to 38*5 c.cm. of 28 p.c. 

 solution of caustic soda in water, makes an excellent basis. The oil is 

 warmed in a water bath and the lye added gradually, the mass being 

 stirred the while. 



The tissue to be imbedded is warmed in a water bath and the soap 

 added as long as it will dissolve. The whole is then poured into a 

 suitable receptacle until sufficiently firm to cut into blocks. These 

 blocks are treated after the paraffin method. Perfect sections 1 micron 

 thick and several feet long are easily obtained. The sections may be 

 treated in the usual way either by sticking them on slides or by im- 

 mersing them in water and dissolving out the soap. But if they are to 

 be fixed to slides in serial order, the ribands are placed on slides 

 previously coated with white of egg and then dried ; they are moistened 

 with xylene, which makes them spread out and adhere. A piece of 

 absorbent muslin is then pressed gently on the sections, and when the 

 xylene has evaporated the muslin is moistened with water. The slide is 

 then cautiously heated to coagulate the albumen and fix the sections to 



* Univ. California Pub. But., ii. (1904) pp. 87-90. 



