100 INTRODUCTION. 



the middle suture of the os frontis, the median line of the 

 uterus, &c. are sufficiently apparent marks of a reunion of the 

 two halves; on the contrary, in the superior portion of the ster- 

 num, in the body of the vertebra, these traces, are, generally, 

 completely effaced. 



108. All the phases through which the human organism 

 passes, correspond with permanent states or conditions in the 

 animal kingdom. We could here accumulate the proofs of 

 this important proposition by drawing a parallel between the 

 human foetus in its various stages of development and the de- 

 grees of organization of the animal scale. Some few exam- 

 ples, however, will suffice. The embryo is at first a mere bud 

 or germ, placed on a vesicle, such, are some of the most sim- 

 ple worms. At a more advanced epoch, it is a little vermiform 

 body without distinct members or head; this is the case with 

 the annelides; still later, the members are equal and the tail 

 protrudes: such is the fact with respect to the greater portion 

 of quadrupeds. In the nervous system, we first see the nerves 

 with their ganglions: such is the case with all the inverte- 

 brata provided with nerves; at a later period we can distin- 

 guish the vertebral and cranial medulla, the tubercles of the 

 latter, and as yet only the rudiments of a cerebrum and cere- 

 bellum : this is the case with fishes and reptiles; still later 

 these last parts increase much more than the tubercles and the 

 encephalon is successively that of birds and the mammalia, 

 until, finally, by the predominance of the cerebral and cere- 

 bellous lobes, it becomes that of man himself. We should see 

 in following the development of the bones, that they are at 

 first mucilaginous, then cartilaginous, afterwards bony and in 

 this state, separated in pieces, which are afterwards welded 

 together; in comparing this development with the state of 

 the bony system in the lamprey, in the cartilaginous fishes 

 and in the oviparous vertebrata in general, we should have 

 another proof of the proposition advanced. It would be the 

 same if we were to pass in review all the genera and all the ap- 

 paratuses of organs. 



109. Man is distinguished from all other animals by the 

 great rapidity with which he passes through the first epochs 



