WET PREPARATIONS. 395 



cuticle from the cutis ; but putrefaction is the best ; for boiling water 

 does not do it so regularly over the whole. 



Of the transparent Preparation of Bones.- — Bones in many animals are 

 a mixture of earth and animal matter ; as the earth is in the form of a 

 powder or calx it is opake. To render such a bone transparent, it is 

 necessary that this earth should be extracted and nothing left but the 

 animal substance. To do this, the bone should be steeped in an acid, 

 with which the earth unites and dissolves. The acid should be so 

 diluted as to have but little effect upon the animal part; however, the 

 weakest acids will, in some degree, affect it, which is of some advantage, 

 as it renders the preparation still more transparent. 



The acid should be diluted so as only to feel a little sharp to the 

 tongue. Perhaps common vinegar is as strong as it shotdd be. Water 

 is commonly the fluid the acid is diluted with, and is as proper as any- 

 thing when the preparation is simply a bone that is to be put into it : 

 but it is sometimes necessary that soft parts are also connected with the 

 bone to complete the preparation. In such cases, to preserve the soft 

 parts from putrefaction, it is proper to dilute the acid with spirit, which 

 preserves the soft parts while the acid is extracting the earth. 



If the quantity of liquid is too small to allow of a sufficient quantity 

 of acid to dissolve all the earth in the bone, then more acid may be 

 added to the same liquid when that which was first put is fully satu- 

 rated, which will be in a day or two. 



Vitriolic acid should never be used, as it does not dissolve the earth of 

 bones, but unites with it in the form of selenites [sulphate of lime]. 

 The marine [nitric] acid should be as pure as possible, or free from any 

 vitriolic acid. 



Of Wet Preparations. — Preparations should never be allowed to have 

 any considerable tendency to putrefaction before they are put into 

 spirits, because the part or piece putrefied does not coagulate so soon, 

 nor so firmly, as the fresh ; therefore you will have the spirits made or 

 kept much longer foul from the oozing of the uncoagulable juices ; but, 

 where it is unavoidable, the spirit should be strong in proportion, espe- 

 cially if the mass be large. If the preparation is made in the summer, 

 and is pretty large, it will be hardly possible to prevent putrefaction 

 before it is properly steeped ; therefore it will require, at first, either 

 more spirit than common, or stronger. 



Of the Colour of Wet Preparations. — As all parts of an animal are 

 nearly of the same colour when deprived of their blood (excepting the 

 skin and some glands, as the liver, which take much of their colour 

 from the juice which they secrete), great care should be taken not to 

 deprive such parts of their blood, which owe much of their distinction 



