288 



THE MICROSCOPE AND ITS REVELATIONS. 



more plainly seen : and it may then be observed that whilst the * red ' 

 corpuscles ( 655) flow at a very rapid rate along the centre of each tube, 

 the ' white ' corpuscles ( 666), which are occasionally discernible, move 

 slowly in the clear stream near its margin. 



685. The Circulation may also be displayed in the tongue of the Frog, 

 by laying the animal (previously chloroformed) on its back, with its head 

 close to the hole in the cork-plate, and, after securing the body in this 

 position, drawing-out the tongue with the forceps, and fixing it on the 

 other side of the hole with pins. So, again, the circulation may be 

 examined in the lungs where it affords a spectacle of singular beauty, 

 or in the mesentery, of the living Frog, by laying open its body, and, 

 drawing forth either organ; the animal having previously been made 

 insensible by chloroform. The tadpole of the Frog, when sufficiently 

 young, furnishes a good display of the capillary circulation in its tail; 

 and the difficulty of keeping it quiet during the observation may be over- 

 come by gradually mixing some warm water with that in which it is 



FIG. 478. 



Capillary Circulation in a portion of the web of a Frog's foot:- 

 tranches; c, c, pigment-cells. 



i, trunk of vein; 6, 6, its 



swimming, until it becomes motionless; this usually happens when it has 

 been raised to a temperature of between 100 and 110; and notwith- 

 standing that the muscles of the body are thrown into a state of spas- 

 modic rigidity by this treatment, the heart continues to pulsate, and the 

 circulation is maintained. 1 The larva of the Water-newt, when it can be 

 obtained, furnishes a most beautiful display of the circulation, both in 

 its external gills and in its delicate feet. It may be inclosed in a large 

 Aquatic-box or in a shallow cell, gentle pressure being made upon its 

 body, so as to confine its movements without stopping the heart's action. 

 The circulation may also be seen in the tails of small Fish, such as the 

 minnow or the stickleback, by confining these animals in tubes, or in 

 shallow cells, or in a large Aquatic-box; 2 but although the extreme 



1 A special form of Live-box for the observation of living Tadpoles, etc., con- 

 trived by F. E. Schultze, of Rostock, is described and figured in the "Quart. 

 Journ. of Microsc. Science," N.S., Vol. vii. (1867), p. 261. 



2 A convenient Trough for this purpose is described in the " Quart. Journ. of 

 Microsc. Science," Vol. vii. (1859), p. 113. 



