310 HENRY H. DONALDSON 



APPENDIX 2 



TECHNIQUE OF PREPARATION 



Theoretically, one should use as a standard for determining 

 the effect of different methods of preparing the skeleton, fresh 

 material which has been cleaned by mechanical methods only, 

 since the immersion of the bones in any solution at room tem- 

 perature or above necessarily alters their weight more or less. 



It is, however, not feasible to make preparations without the 

 use of some solvent for the connective tissue, and in the prepa- 

 ration of all of the skeletons included in this study a solution 

 of commercial 'Gold Dust Washing Powder' was used. The 

 approximate composition of this is: Sodium carbonate, 45 per 

 cent; soap powder, 30 per cent; water, 25 per cent. 



The rat was roughly dissected and the parts placed in 50 to 

 200 cc. of a hot Gold Dust solution in tap-water. For mature 

 rats a 2 per cent solution at 96°C. was used for an hour, more or 

 less, the material being watched and tested. The object to be 

 attained was a complete softening of the attachments of the 

 muscles, so that they could be readily removed with the bone 

 scraper, or brush used for cleaning the bones. The younger the 

 rat the weaker was the solution, the lower the temperature 

 used, the shorter the time and the more careful the watching. 



When bones are immersed in the macerating fluid, which acts 

 mainly on the surface, it seems probable that those which are 

 large, dense, mature, or cubical will be less affected than those 

 which are small, porous, young, or flat, and our tests show this 

 to be the case. We have therefore chosen as typical and as 

 giving values which can be applied to the skeleton as a whole, 

 the humerus and the femur. 



When the macerated humerus and femur from one side of a 

 rat were compared with those from the other side, freshly cleaned 

 by cutting and scraping, but not macerated, the method of 

 maceration here used causes a loss in the weights of these bones 

 as given in table 34. 



The data in table 34 are given according to the body weights 

 of the rats, these latter being considered normal to the age. 



