INTRODUCTION. 3 



knowledge of the structure of nerve fibres, their origin and termina- 

 tion, especially in muscle, their relations within the ganglia, and 

 even the structure of muscular fibre itself. For the study of 

 reproduction and development the frog has, next to the chick, 

 afforded the most important material : one need but refer to the 

 investigations on impregnation from the time of Spallanzani to 

 that of Newport ] , the phenomena of cleavage, and many others. 



Thus with progress of time the field in which the frog has been 

 submitted to observation and experiment, whether for the demon- 

 stration of established facts to students or for the solving of new 

 problems, has vastly increased, and this batrachian has indeed be- 

 come, as we have stated, the physiologist's domestic animal. 



That, for these manifold uses, a more exact anatomical know- 

 ledge of the frog is very necessary is self-evident. The majority of 

 students commencing the study of physiology have little more than 

 a superficial knowledge of the sciatic nerve and the leg-muscles ; at 

 most, of the spinal cord and its nerve-roots ; and only acquire any 

 further knowledge in a disconnected manner. For this they can 

 scarcely be reproached, the literature of the anatomy of the frog 

 being so widely scattered in monographs and journals that reference 

 to it involves the expenditure of much time. This attempt, there- 

 fore, to produce a complete anatomy of the frog, based throughout 

 upon my own observations, cannot be considered superfluous ; it is 

 rather to be feared it may be thought insufficient. 



The European frogs 2 alone are treated of in the following 

 description, i.e. the two species, Rana esculenta, L., and R. fempo- 

 raria, L., the former being more particularly described, though 

 such differences in structure as occur are noted. This is not 

 the place to discuss the exact systematic characters of the two 

 species, yet they cannot be ignored entirely. The species were, 

 from their habitats, long ago distinguished by C. Gessner 3 , and 

 named Rana rubeta, s. gibbosa, the garden or grass-frog, and Rana 

 aqitatica, s. innoxia, the water-frog ; at least, from his figure, the 

 former can be no other than R. temjioraria, though Gessner, 



1 It may be well to remind the reader that this introduction was written in 1864. 



2 For purposes of comparison other than European frogs were examined, especially 

 American species of Sana, for which I am indebted to the kindness of my much 

 esteemed friend Agassiz. These were Rana Catetlyana, Shaw (S. mugiens, Catesby 

 E. pipiens, Harlan) ; R. sylratica, Leconte; S. clamitatis, Daudin ; B. palustris, 

 Leconte ; R. halecina, Leconte. To these, however, no further reference will be made 

 in the text. 



3 C. Gessner, Thieibuch. Zurich. Fol., p. 157. 



B 2 



