896 SUMMARY OF CUERENT RESEARCHES RELATESTG TO 



rize with weak alum solution for a period of several hours to some 

 days. Nuclei and cell boundaries are well shown. Cut in paraffin. For 

 macerating, a 2 or 3 per cent, solution of chromate of potash, or it 

 may be concentrated and diluted with a weak oxalic acid solution or 

 Miiller's fluid. 



Fresh material is ready in a few hours ; hardened material in a 

 few weeks. It is recommended to dissociate the macerated and stained 

 specimen when in section, and to separate its elements by tapping 

 on the cover-glass. 



Method of Softening Chitin.* — Dr. Looss describes a new method 

 of dissolving the chitinous skeletons of Arthropoda, &c. The reagents 

 used are hypochloride of potassium and sodium; the latter can be 

 purchased in chemists' shops under the name of Eau de Laberraque. 

 The percentage of the solution has not been definitely settled. The 

 chitinous skeletons of insects are rendered completely transparent, 

 and the nerves and muscles uninjured by the use of the reagent 

 diluted 4-6 times with water. 



Demonstrating Nerve-end Organs in the Antennse of Myrio- 

 pods.j — In order to demonstrate the origin and the articulation of the 

 olfactory bulb in the antennse of Chilognatha, Dr.B. Sazepin first washes 

 the antennse in alcohol, and then, in order to remove the pigment from 

 the chitinous tissues, immerses in chloroform to which one drop of 

 strong nitric acid has been added. After being placed in absolute 

 alcohol they are treated with 1/2 per cent, solution of osmic acid. The 

 nervous tissue becomes brown in about 20 hours. The processes 

 previous to cutting are to place the antennae in absolute alcohol and 

 next in picric acid for a day. After washing frequently in 75 per 

 cent, spirit, transfer to absolute alcohol and stain with Grenacher's 

 alum-carmine. Wash for a whole day in water; for another in 

 75 per cent, spirit ; then absolute alcohol, chloroform, paraffin, 

 and cut. 



Sources of Error in the Examination of Fresh Tissues.^ — Dr. 

 Heller draws attention to two sources of error in the examination of 

 fresh tissues, each of which can, however, be obviated by adopting 

 proper precautions. 



1st. The red blood-corpuscles are in a great many cases destroyed 

 by the cold temperature when the sections are cut with a freezing 

 microtome. This can, however, be prevented by placing the pieces 

 of tissue, before cutting, for a short time in a weak solution of 

 bichromate of potash. 



2nd. When a large number of sections have to be examined, a 

 development of micro-organisms may occur before there is time to 

 carry out the examination. This, too, can be prevented by placing 

 the sections in salt solution (3/4 per cent.) to which 1 per cent. 

 chloral hydrate has been added. An addition of 1/2 per cent, chloral 



* Zool. Anzeig., viii. (1885) pp. 333-4. 



t Mem. Acad. Imp. Sci. St. Petersbourg, xxxii. (1884), 20 pp. and 3 pis. 



X ZeitBchr. f. Wiss. Mikr., ii. (1885) pp. 47-8. 



