ZOOLOGY AND ROTANY, MICROSCOPY, ETC. 633 



(2) Preparing- Objects. 



Preparation of Ascaris Embryos.*— To obtain microscopical pre- 

 parations showing the various stages in the early development of Ascaris 

 meiiaJocephaJa^ H. Joseph recommends the following procedure. Two 

 small paraffin cylinders, of like size and dimensions, are connected 

 together by two thin (1-2 mm. diameter) glass rods, about 2 cm. in 

 length, and placed 1 cm. apart. A sort of flat bobbin or spool is thus 

 obtained. The genital tube is taken from an Ascarid and loosely 

 unravelled. It is unnecessary and unwise to attempt a complete 

 unravelling. The tube is then wound round the glass rods in a flat 

 spiral. The end of the tube is fixed between two previous coils to 

 prevent unwinding. The whole apparatus is put in the fixing fluid, 

 washed, hardened, and embedded in the usual way. In the paraffin 

 bath the ends of the bobbin will melt, and the glass rods may be easily 

 withdrawn. Sections parallel with the coils will show progressive stages 

 of development of the contained embryos. 



(3) Cutting-, including- Embedding- and Microtomes. 



Microscopical Examination of Skin and Leather. t — G. Abt has 

 examined microscopically, by means of sections, skins and leathers, for 

 the purpose of ascertaining the changes which are associated with the 

 " salt-spots." The spots are very detrimental and lower the price of 

 leather, especially calf, so that spotty skins have to be blacked to conceal 

 the defects. 



For skin the following fixatives are recommended : (1) saturated 

 aqueous solution of picric acid 70, formalin 40 p.c. 10, acetic acid 1 ; 

 (2) chromic acid 0*4, acetic acid 1*5, formalin O'l, water 100. 



After 24 to 48 hours the pieces, which should not exceed 5-6 mm. 

 thick, are washed, dehydrated, and embedded in paraffin. The sections 

 are then stained in various ways and by means of various procedures, 

 such as magenta followed by picric acid and indigo carmin ; hagma- 

 toxylin and eosin ; safranin ; thionin. 



Tanned material does not require fixation ; the pieces are merely 

 washed and then run through to make paraffin sections, which are 

 stained in the usual way. 



In order to demonstrate tannin, 1 p.c. iron alum is used ; this im- 

 parts to the impregnated fibres a grey to blackish-brown hue. Elastic 

 fibres were stained with orcein (0*4 p.c. in 80 p.c. alcohol, with an 

 equal bulk of 4 p.c. hydrochloric acid in SO p.c. alcohol). 



Micro-organisms were detected by means of Gram's method, but if 

 Gram-negative the results were poor, the least indifferent being ob- 

 tained by means of thionin and washing with acetic acid, or with 

 magenta-red followed by picro-indigo carmin. 



Reconstruction Methods. J — Y. Fedorow uses ozokerite (yellow 

 ceresin) instead of beeswax, for reconstruction work. The physical 



* Zeitschr. -wiss. Mikrosk., xxx. (1913) pp. 181-4. 



t Bull. Soc. d'Encouragement pour I'lndustrie Nationale, cxix. (1913) pp. 

 646-66 (2 pis. and 7 text figs.^ . 



t Zeitschr. wiss. Mikrosk., xxx. (1913) pp. 178-181. 



