324 CYTOLOGICAL METHODS. 



Etherisation. Three per cent, alcohol, or 3 per cent, ether, 

 may be used in a similar way. These reagents cause no 

 obstruction to the processes of cell-division, and are useful, 

 but their action as anaesthetics is inconstant. 



Indifferent Media. One per cent, salt solution, iodised serum, 

 syrup, cold water ( + 1 C.), and warm water (35 40 C.). 

 The tail may be excised from the living animal and studied 

 for a long time in these media (PEREMESCHKO, Arch. f. mik. 

 Anat., xvi, 1879, p. 437). 



Perhaps (FLEMMING, ibid., pp. 304 et seq.) the very best 

 subject for these studies is Salamandra. The adult offers 

 for study the thin transparent bladder ; in the larva the gills 

 and caudal "fin" may be studied in the living state. The 

 gills are difficult to fix in position for observation, and are 

 obscured by pigment. In the fin there is always a spot, near 

 to the hind limbs, that is free from, pigment ; and on lightly 

 coloured larvae other such spots may be found on the ventral 

 half of the fin and on the lateral line. On a flat-finned larva 

 it is possible to study these spots with high-power glasses. 



The larva may be fixed in a suitable cell, or wrapped in 

 moist blotting-paper, or may be curarised ; or the tail may be 

 excised. (It is preferable to cut through the larva close in 

 front of the hind limbs.) 



A favorable object for preparation is found in the gill-plates, 

 delicate laminae that are to be found attached to the gill-car- 

 tilages on the mouth side. 



The lungs, parietal peritoneum, and mesentery of the larvae 

 are also very favorable objects for preparations (see FLEM- 

 MING, Arch. f. mik. Anat., xxxv, 1890, p. 275 ; and xxxvii, 

 1891, pp. 249 and 685). To prepare the lungs the larva, 

 which should be of not more than 4 cm. length, should be 

 killed by immersion in chromo-aceto-osmic acid, the body- 

 cavity cut into, and the viscera gently drawn out and exposed 

 to the action of the liquid, care being taken not to let the 

 lungs get into folds. After fixation they should be carefully 

 got on to a slide, and a small strip removed from their mar- 

 gins on either side by means of a scalpel, after which the two 

 walls may be separated from each other, and utilised as thin, 

 flat preparations. 



Another excellent object is the intestine of the adult, of 

 which sections may be made by the paraffin method, as recom- 



