relative to Natural History, 319 



budget of nature is fixed ; but she is free to dispose of parti- 

 cular sums by any appropriation that may please her. In 

 order to spend on one side, she is forced to ceconomize on the 

 other, and nature can therefore never run in debt nor become 

 bankrupt." It is easy here to recognise the principle put forth 

 by M. Geoffroy Saint Hilaire under the name of the balance 

 of organs. 



These considerations may be applied in two ways ; either in 

 the comparing of beings with one another, and the result of this 

 observation is to show the general type modified by the above 

 law according to the part which the species acts in nature and 

 the medium in which it dwells ; or in comparing with each 

 other the different parts of the same being, a study in which 

 the same balance is perceived, and which leads to generaliza- 

 tions of a more difficult character and included generally 

 under the name of the law of homology. We shall here leave 

 these discussions concerning the type, and shall not follow 

 the author in the applications he makes of them when he pro- 

 duces the model of an osteological type for the Mammiferae, 

 and analyses the variations of the bones and the characters by 

 which they may be known ; an analysis of high importance 

 from its applications, but which would carry us beyond our 

 intended limits. 



Under the second head, that of special labours, we always 

 discover the same drift and the same philosophical views. 

 One of the most generally known is the discovery of the in- 

 termaxillary bone in man. It is known that most of the Mam- 

 miferae have both sides of the upper jaw formed of two bones, 

 the one external and largest, which contains the molary and 

 canine teeth, and which is the maxillary properly so called; the 

 other internal, smaller, which contains the incisors, and which 

 has received the name of the incisive or intermaxillary bone. 

 These two bones are not separate in man at the adult age. 



The naturalists of the past century had eagerly laid hold of 



ment of the ribs brings with it the disappearance of the feet. This latter exam- 

 ple has even this remarkable circumstance, that all the transitions are to be 

 seen, at first in the Scincidce, which have more ribs than the lizards and 

 smaller feet ; then in the Sepsidcs, which have almost the ribs of serpents 

 and the rudiments of feet ; and lastly in Anguis, which comes still nearer to 

 the serpents, and whose limbs are not externally visible. 



