832 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tions, precipitates or albuminates which arc indistinguishable from natural 

 pigment, and for which they have been repeatedly mistaken. 



Preparations hardened in the above manner can be made into very 

 thin sections, and are easily stained with anilin colours, but arc not 

 susceptible of being treated by Weigert's hoematoxylin method. Safranin 

 stains the chromolejjtic substance very beautifully. Over the freezing 

 and alcohol hardening the sublimate alcohol method has the important 

 advantage of not altering the contour of the cells. 



With regard to the pigment produced along the vessels and in the 

 nerve-cells, it was found that it disappeared entirely therefrom after 

 long immersion in warm distilled water. Alcohol and ether had no 

 effect except to change the black into brown. Caustic potash dissolved 

 in spirit or 25 per cent, acetic acid had no action. 25 per cent, nitric 

 acid destroyed it slowly, while a 30 per cent, solution of iodide of 

 potassium converted it into a yellow-brown, and the strong Lugol 

 solution quite effaced it in five minutes. Cold distilled water dissolves 

 it after several weeks. 



This artificial black pigment, according to the author, is either a 

 comjiound of a metal and of albumen, or the result of a simple 

 mechanical saturation of the tissue, probably the former. 



Preparation of Criodrilus lacuum.* — In his investigation into the 

 structure of Criodrilus lacuum Dr. A. Collin examined living specimens, 

 and sections prepared with Jung's microtome. Hardening was generally 

 effected by a mixture of one part of corrosive sublimate and one part 

 70 per cent, alcohol. The pieces were left in the mixture for from 

 thirty minutes to one hour, according to their size. They were then 

 placed in water or weak spirit for some time, dehydrated by alcohol and 

 chloroform, and imbedded in paraffin. Neither chromic nor picric 

 acids are adapted for hardening worms. Specimens were killed with 

 chloroform, and died without any violent muscular contraction. The 

 staining of the pieces was best effected by ammoniacal picrocarmine ; 

 the sections were successfully stained by methylen-blue or borax- 

 carmine wdth acetic acid ; the former coloured the ganglionic cells, and 

 the latter the nuclei of the epithelia and of the connective tissue. 

 Macerations were effected partly with Miiller's solution and partly with 

 potash. 



Method of Preparing Tegumentary Filaments of Flagellata.f — 

 M. J. Kiinstler refers to the well-known fact that flagellate Infusoria, 

 when treated with certain reagents, become covered with a variable, 

 though often very considerable quantity of filaments, which are sometimes 

 very long, and that an analogous phenomenon may be observed in ciliate 

 Infusoria. In the latter, however, each filament is derived from a small 

 refractive capsule, placed in the peripheral layer of the body. Till their 

 homology shall be disproved all these processes may be called tricho- 

 cysts. The best way to prepare them is to treat perfectly fresh speci- 

 mens with concentrated osmic acid, so as to fix them, and then to colour 

 them very slowly by diffusion by means of picrocarminato of ammonia. 

 A less delicate method, by which one can at least determine whether or 

 no a given species has trichocysts, is to fix a specimen with concentrated 



* Zeitsphr. f. Wiss. ZooL, xlvi. (1888) pp. 474-5. 

 t Comptes Rendus, cvii. (1888) pp. 138-9. 



