CIRCULATION IN FROG AND TADPOLE. 



735 



575. The Circulation may also be displayed in the Tonque of the 

 Frog, by laying the animal down on its back, with its head close 

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



Fig. 393. 



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

 Vein ; b, b, its branches ; c, c, Pigment-cells. 



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

 the other side of the hole with pins. This method, however, is so 

 much more distressing to the animal, that its employment seems 

 scarcely justifiable for the mere purpose of display : while nothing 

 but some anticipated benefit to science can justify the laying-open 

 of the body of the living animal, for the purpose of examining the 

 circulation in its Lungs or Mesentery. 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 overcome by gradually mixing some warm 

 water with that in which it is swimming, until it becomes motion- 



