2 INTRODUCTORY LETTER. 



reeled my researches to the class of Reptiles. I commenced 

 by representing in accurate designs the most interesting 

 species of this little understood class of beings, and it is 

 thus that by degrees was formed a series of anatomical 

 and zoological drawings, one part of which I now publish, 

 and shall cause the rest to follow Avhen the numerous dif- 

 ficulties that at present impede the publication of my re- 

 searches shall have been wholly removed. 



I have abridged in my book all the observations which 

 I have been able to make in Oi)hiology. Yet, the state in 

 which this part of science exists has constrained me to de- 

 viate in many respects from my original plan, and to defer 

 the publication of the anatomical researches, Avhich are 

 the basis of mv labours. IIow could mv readers, for in- 

 stance, have comprehended me if I had spoken to them of 

 the numerous new species, the discovery of which is due 

 to our travellers ? IIow could they explore the way through 

 systems containing such a vast number of species, often 

 piu'ely nominal or more than once introduced ? What 

 work could we recommend to serve as a guide through this 

 labyrinth ? I do not know any such. 



These reasons, joined to several others, have decided 

 me on giving to my book the form under which it now ap- 

 pears. In the mean time, in conceivmg this new plan, it 

 presented difficulties similar to those to which I have al- 

 luded. To what figures could I refer to complete my de- 

 scriptions ; and how fe^v naturalists can even consult those 

 expensive works in which they are contained ? Besides, 

 no study offers more difficulties than the comparison of 

 different species of sei'pents, — animals which so nearly re- 

 semble each other in the form of their bodies, that one is 

 often obliged to have recourse to the structure of the head, 

 to obtain for them distinctive characters. 



These motives have induced me to delineate on the same 

 plate the figures of all the species of each genus, or, at least, 

 those of the most remarkable. On comparing these por- 

 traits, one will readily be able to seize the peculiar phy- 

 siognomy of each, and thus to distinguish nearly allied 

 species. 



The word Physiognomy is here used in its ordinary ac- 



