42 METAMORPHOSES OP MAN 



CHAPTER V. 



TRANSFORMATIONS WHICH MAMMALS UNDERGO AFTER THEY 

 HAVE LEFT THE EGG. 



The development of mammals is, as we have seem 

 exceedingly energetic in the commencement; then 

 gradually the organs appear in their proper order, 

 assume their distinctive forms and proportions, and 

 take up their right positions. The embryo, in fact, 

 has become a foetus, and has now strength enough to 

 make its own way in the world. Finally, it is born ; 

 its lungs perform their function, its digestive apparatus 

 discharges its duties, and its circulation is complete. 

 Does this last step leave the organism, which has 

 already undergone so many changes, in a state of rest ? 

 We saw in the first chapter how the balance answered 

 this question, and here again we must employ accurate 

 instruments in extending our observations to the 

 animal kingdom. Is the infant in the same condition 

 as the youth, or the adult as the aged ? Is it not pro- 

 bable that at every period of life the form and propor- 

 tion of an animal undergo alterations ? And, unless 

 we admit that our organs are the seat of perpetual 

 changes and modifications, how shall we explain these 

 alterations ? 



Of all the periods mapped out by the successive 

 external features of an animal, there are none which 

 are more remarkable, viewed from our stand-point, 



