INTRODUCTION. 



THERE is no occasion, now-a-days, to offer a lengthened apology 

 for devoting a treatise solely to the anatomy of the frog, which enjoys 

 the doubtful honour of being, /car' ^o\^v, the physiological domes- 

 tic animal. It is kept in every physiological laboratory, and is daily 

 sacrificed in numbers upon the altar of science. The physiologist 

 has recourse to it, not only to obtain answers to new questions, but 

 for the sake of demonstrating easily and quickly the most im- 

 portant known facts of the science. These unlucky batrachians are 

 to be had in any number, and are specially adapted for experimental 

 investigation : they have consequently fallen under a harsher tyrant 

 than the stork in the fable, and their prophetic outcry in the 

 frog-chorus of Aristophanes, 8eim Tei<ro'/zefT0a, has been literally 

 fulfilled. 



As the history of the most important physiological discoveries is 

 closely related with the employment of the frog in physiological 

 research, it will not be without interest to review briefly the 

 history of its use in scientific, especially in physiological, investi- 

 gations, and to record the services which it has already rendered 

 to science. Swammerdam (1637-1685), as du Bois-Reymond justly 

 remarks, was the first to make known the frog as an important 

 means of research ; he says concerning it : ' An den Thieren, die 

 das heisseste Blut haben, ist die Bewegung der Muskeln nicht so 

 merklich oder halt vielmehr nicht so lange an, als an Thieren die 

 mit kalterem Blute begabt sind. Dergleichen sind die Fische und 

 viele andere Wasserthiere, wie auch sole-he, die so wohl im \Vasser als 

 auf dem trocknen Lande leben konnen. Deswegen habe ich inson- 

 derheit mit dem Frosch meine Yersuche angestellt. Denn an diesem 

 Thiere sind die Sehnen sehr sichtbar und lassen sich leicht entdecken 



