INTRODUCTORY 13 



poured off, and a new supply, prepared in the same way, is substituted. 

 After boiling again for half an hour, the bones are cooled in water 

 and the muscles are picked off. If there be any difficulty in removing 

 the soft parts, the bones should be boiled again for a short time, and 

 then brushed clean with a stiff brush. Finally, when perfectly clean, 

 to remove grease, they are boiled for half an hour in a mixture of 

 equal parts of the pure Soap Solution and water, after which they are 

 washed in clean water and laid out to dry. 



It must be remembered that if the skeleton of a kitten is to be 

 prepared, the boiling must be done carefully, or all the epiphyses of 

 the bones will become loose. If, on the other hand, the bones of the 

 skull of an old animal are to be separated, the boiling must be carried 

 still further. 



To make the bones still whiter by removing every trace of grease, 

 thev mav be soaked for several weeks in ether or benzine. Avoid 



/ , 



danger from fire. 



It will be useful to have for comparison a second skeleton whereof 

 the bones are articulated in their proper position. This skeleton 

 may be purchased from a dealer in natural history supplies, or the 

 student may prepare what is known as a natural skeleton, one in 

 which the bones are held together by their natural ligaments. To 

 make such a skeleton the student proceeds as before, except that the 

 skull, ribs, tail, and posterior limbs are not separated from the vertebral 

 column and the boiling in soap solution is carried only far enough 

 to permit of the removal of the muscles. The ligaments which bind 

 the bones together are carefully preserved, and the whole skeleton is 

 arranged on a wire support, in a natural position (Fig. 3), and 

 permitted to dry. The anterior limbs, which are attached to the trunk 

 by muscles only, must be cleaned separately and afterwards secured in 

 place by wires. 



The student should also, for the sake of comparison, have access to 

 a human skeleton. 



NUMBER OF BONES IN THE SKELETON. 



The number of bones in the skeleton depends upon the age of the 

 animal. In a young specimen the number of distinct osseous pieces is 

 much greater than in the adult ; the epiphyses are not yet united to 

 the diaphyses, and bones, which in the adult are the result of the 



