PRACTICAL ANATOMY. 385 



In large animals we are obliged to have recourse only to parts to 

 make preparations of, and for convenience ; but in small ones we are led 

 to preserve the whole, and expose as much as possible ; which breaks 

 in upon the arrangement and classing of specimens : but it is some- 

 what like nature herself; one property belonging to more animals than 

 one 1 . 



On making Anatomical Preparations, by Injection, fyc. 



The proper house. — A skylight is very improper : a side- or front- 

 light should be preferred. 



The proper place for keeping Preparations. — Both wet and dry should 

 be kept in a cool place. If on a ground floor, and towards the north, 

 so much the better ; as the evaporation from the wet, and the throwing 

 out of the wax from the dry, at cut parts, will be less. 



The proper subjects.— Animals which have been bled to death are 

 not so fit for minute injections as those which have died a natural death, 

 because the vessels contract to adapt themselves to the quantity of blood 

 contained in the body while bleeding ; and all the muscular parts con- 

 tract after death ; therefore, if there is no blood in the arteries, they 

 will become almost impervious. In such cases, steep the parts for some 

 time till a species of putrefaction begins to take place. The parts 

 should likewise be gently squeezed, to relax the muscular contraction of 

 the vessels. These two last circumstances should be punctually attended 

 to ; for if it is a part of a newly dead animal, it will not allow the in- 

 jection to go so far as when the animal has been dead some time : but 

 great care should be taken not to allow putrefaction to go too far. 



Parts of bodies that are to be injected and shown in their natural 

 form, should be parts of young and healthy subjects; as they will be 

 less altered from their form than by disease, and the vessels will better 

 bear the injection. If possible, the water that preparations should be 

 steeped in should be distilled, for it preserves animal bodies above six 

 times longer from putrefaction than common water ; and by this means 

 the parts will have time to become more free of blood, especially thick 

 parts. If not distilled, it should be clear and often changed. If the 

 part be suspended near the surface of the water, so much the better, as 

 the part will not be allowed to soak in its own blood, which will gravi- 

 tate to the bottom. 



In all injections use a pipe as large as you can get into the vessel, as 



1 [The degree in which Hunter overcame these impediments in carrying out his 

 great idea of a physiological collection of anatomical preparations, may be estimated 

 by a study of that part of his museum containing his dissections of animals of every 

 class, and of plants; or of its Catalogue, ' Physiological Series,' 5 vols. 4to. 1833— 1840.] 



2c 



