METHODS — PAL^ONTO LOGICAL 41 



While, save in the rarest instances, only the hard parts of 

 fossil mammals remain to testify of their structure, very im- 

 portant information as to the size, form and external character 

 of the brain may be secured from ''brain-casts," which may 

 be natural or artificial. The pressure of the mud, sand or 

 other material, in which the fossil was embedded, filled up all 

 openings in the skeleton and, as the brain decayed and dis- 

 appeared, its place was taken by this material, which subse- 

 quently hardened and solidified and quite accurately reproduces 

 the external form and character of the brain. When a fossil 

 skull is exposed and shattered by weathering, the natural 

 brain-cast often remains intact, and a great many such speci- 

 mens are in the collections. An artificial cast is made by saw- 

 ing open the cranial cavity, cleaning out the stony matrix 

 which fills it and then pouring liquid gelatine or plaster of 

 Paris into the cavity. These artificial casts are often quite 

 as satisfactory as the natural ones. 



As has been shown above, the history of the mammals is 

 recorded, save in a very few instances, in terms of bones and 

 teeth and, to the uninitiated, it might well seem that little 

 could be accomplished with such materials. However, it is 

 the task, and the perfectly feasible task, of palaeontology to 

 make these dry bones live. It is a current and exceedingly 

 mischievous notion that the palaeontologist can reconstruct 

 a vanished animal from a single bone or tooth and, in spite of 

 repeated slayings, this delusion still flourishes and meets one 

 in modern literature at every turn. No doubt, much of the 

 scepticism with which attempts to restore extinct animals 

 are met by many intelligent people is traceable to the wide- 

 spread belief that such off-hand and easy-going methods 

 are used in the work. So far from being able to make a trust- 

 worthy reconstruction from a few scattered bones, competent 

 palaeontologists have been sometimes led completely astray 

 in associating the separated parts of the same skeleton. More 

 than once it has happened that the dissociated skull and feet 



