90 METAMORPHOSES OF MAN 



replace them by lungs ; and at the necessary time, 

 a set of changes takes place analogous to those we 

 have already described. The vascular tufts are 

 atrophied, and the lungs, which till now were solid 

 and rudimentary, open up and increase in size. The 

 circulatory organs are correspondingly modified. The 

 calibre of the large branchial vessels is diminished, 

 and the pulmonary trunks increase in number and 

 diameter. Later on, the solid parts of the branchial 

 apparatus disappear also, the bones and cartilages 

 being gradually reabsorbed. Eventually the alteration 

 is fully accomplished, and there remains not the 

 slightest trace of the former branchial apparatus. In 

 this instance, not only has there been transformation 

 and substitution, but an actual metamorphosis has 

 occurred ; for the respiration, which was aquatic before, 

 has become atmospheric, and, strictly speaking, the 

 animal from having been a fish has been converted 

 into a batrachian. 



If we examine any particular apparatus, we shall find 

 it also presenting many curious phenomena in the 

 course of its development. We shall find that as the 

 herbivorous habits give place to carnivorous ones, the 

 digestive apparatus undergoes a change adapting it 

 to the new form of diet. The mouth increases in size 

 and gape; the little beak-organs, or more correctly, 

 the horny lips, are replaced by teeth, which are 

 attached to the palatine arch, and not to the jaw; 

 the intestine, which before was long and almost 

 cylindrical, becomes shorter, and is inflated in certain 

 portions of its length; and the abdomen, which had 

 been almost spherical, becomes thin and slender. 

 The metamorphosis may now be seen in its entire 



