48 PRACTICAL HISTOLOGY. 



heart, and not by merely snipping a piece off the tail 

 and collecting; the drop which exudes, for in this case 

 it is very apt to become mixed with the acrid secretion 

 from the cutaneous glands. There are, in addition, 

 two reactions for which newt's blood is particularly 

 well adapted, viz., the actions respectively of boracic 

 acid and carbonic acid upon the red corpuscles. 



Preparation 15. Action of Boracic Acid. 

 The boracic acid is used in solution in water (two 

 parts per cent.), and the preparation of blood having 

 been made in the usual way, with or without addi- 

 tion of salt solution, a drop of the boracic acid solu- 

 tion is placed at the edge of the cover-glass and 

 allowed slowly to mingle with the blood. If the 

 first stages of the reaction are fortunately observed 

 it will be seen that the colored part of the corpuscle 

 is becoming collected towards the centre of the cor- 

 puscle and accumulated around the nucleus, often 

 remaining, however, at first adherent here and there 

 to the circumference of the corpuscle, and shrinking 

 away at the intermediate points, so as to present 

 somewhat of a stellate figure. 1 But soon it is en- 

 tirely withdrawn and collected around the nucleus, 

 which has become rounded, and is nearly concealed 

 by the coloring matter. The corpuscle, now decolor- 

 ized, has also in many cases become circular, and the 

 colored nucleus is generally shifted to one side, and 

 eventually altogether extruded. 



Preparation 16, To investigate the action of 

 carbonic acid gas the blood must be prepared in a 

 moist chamber, like that used for chloroform vapor 

 (Fig. 11). If the preparation is very quickly made 

 the nucleus in many of the red corpuscles cannot at 

 first be distinguished, for in the entirely unaltered 

 state it possesses as nearly as possible the same index 

 of refraction as the rest of the corpuscle. But when 

 carbonic acid gas, generated in a suitable apparatus 



1 Water and various other reagents may, in the first instance, 

 have a somewhat similar effect. 



