THE BLOOD. 43 



acid gas is generated. Fig. 19 illustrates a gas or moist cham- 

 ber of the same general character, and devised by Dr. J. H. 

 Hunt, of Brooklyn. Take a large gallon flask, fill it partly 

 full of pulverized marble-dust, attach it by means of a rubber 

 tube through a perforated stopper to a Wolff's bottle, which 

 latter must be connected with the moist chamber. Now gener- 

 ate the carbonic acid gas in the flask by pouring muriatic acid 

 upon the marble-dust. When the gas is being evolved it will 

 be known by the ebullition of the water in the Wolff's bottle. 

 Now place the moist chamber upon the stage of the micro- 

 scope. Take a drop of newt's blood, dilute it with serum or an 

 indifferent fluid, and mount it upon a glass cover, which invert 

 over the well, first seeing that the edge of the cover is oiled, so 

 that it will remain in place. Now connect the tube of the moist 

 chamber with the tube of the gas-generator, and the carbonic 

 acid gas will enter and pass through the chamber. The rapidity 

 with which the current moves may be regulated by a spring 

 clip. As soon as the gas enters, the central body or nucleus 

 becomes distinctly visible, and is surrounded by a yellow halo ; 

 when, however, the gas is withdrawn and atmospheric air 

 is admitted, the nucleus and colored zone disappear. This 

 double experiment may be repeated a number of times. Finally 

 a point will be reached where all action will cease. This cen- 

 tral body, under such circumstances, has been called the zooid, 

 and the corpuscles proper the oiTcoid (Bruecke). 



Action of acids upon tJie blood. Acetic acid is commonly 

 used in observing the changes that are produced by an acid 

 solution. 



Take the ordinary dilute watery solution of acetic acid 

 (1 per cent.) so much used in laboratories, add a drop of it to 

 an equal amount of frog's blood. The red globules instantly 

 exhibit nuclei. The colorless globules also cease their motion, 

 if any has existed, and they become granular and shrivelled. 

 The term granular is used merely in a relative sense and has no 

 special reference to granules whether present or not, but merely 

 to an appearance that has already been explained. 



These phenomena are more marked if the solution is con- 

 centrated. The red bodies, also, in such case, are apt to crack 

 and split up. A good way of determining the proper strength 

 for the ordinary acetic acid solution is to pour a little into an 

 ordinary watch-glass, and then add chemically pure acetic 



