290 EMBRYOLOGICAL METHODS. 



Doubtless the best fixative yet made known for ova furnished 

 with their capsules will be found to be that of CAENOY and LEBRUN, 

 86 (La Cellule, xiii, 1897, p. 68). After fixation the ova are carefully 

 brought into 80 per cent, alcohol, in which they are preserved. 

 Imbedding should be carefully done as recommended for the ova of 

 Amphibia ( 602), but they ought not to remain in the pure paraffin 

 for more than a minute to a minute and a half. But these authors 

 prefer the celloidin method. At least six weeks' soaking in the 

 different strengths of celloidin will be necessary to ensure penetration. 

 They stain with iron hsematoxylin. 



ZUR STRASSEN (Arch. Entwickelungsmech., iii, 1896, p. 29) fixes 

 for twenty-four hours in a mixture of 4 parts 96 per cent, alcohol 

 and 1 part acetic acid, brings into pure alcohol, stains with hydro- 

 chloric acid carmine, and brings gradually into glycerin. 



Similarly Z,ojA(Arch. mik. Anat., xlvii, 1896, p. 218) and ERLANGER 

 (ibid., xlix, 1897, p. 309). Zoja stained with Bismarck brown and 

 examined in dilute glycerin ; Erlanger made paraffin sections and 

 stained with iron hsematoxylin. 



KOSTANECKI and SIEDLECKI (ibid., xlviii, 1896, p. 184) employed 

 concentrated sublimate solution, or 3 per cent, nitric acid or mixtures 

 of these two, for ovarian ova. 



VAN BENEDEN and NEYT (Bull. Acad. Belg., 1887, p. 214) took 

 equal parts of alcohol and acetic acid. BOVERI (Jena Zeit., xxi, 

 1887, p. 423) fixed in his picro-acetic acid, 95 a clearly inadequate 

 method. GULICK (Arch. Zellforsch., vi, 1911) has " fixed " ova of 

 Heterakis for twenty-two hours in one-third saturated picric acid 

 with 3 per cent, of glacial acetic acid, and had them develop in 

 alcohol of 70 per cent, to stages representing a normal development 

 of several weeks. 



BORING (Arch. Zellforsch., iv, 1909, p. 121) spreads ova of Ascaris 

 on a layer of Mayer's albumen on a slide, sets the albumen with 

 a drop of formol, fixes with 4 parts of alcohol to 1 of acetic acid, 

 stains in alcoholic hydrochloric acid carmine, and mounts in 

 glycerin. 



ARTOM (Zeit. wiss. Mik., xxv, 1908, p. 5) freezes segments of the 

 uteri of Ascaris in salt water, and cuts them with the freezing 

 microtome into disks 30 //, thick, and fixes these with divers 

 liquids. 



CERFONTAINE (ibid., xxix, 1912, p. 305) brings fixed ova from 

 alcohol into absolute alcohol with 1 per cent, of clove oil, evaporates 

 this down to one-tenth, puts into absolute alcohol with 5 per cent, of 

 clove oil, evaporates again down to one-tenth, then into the same 



