24 PROCEEDINGS OP THE ACADEMY OP [1884. 



ON SEMPERS METHOD OF MAKING DRIED PREPARATIONS. 

 BY DR. BEN J AM UN SHARP. 



Although this admirable method has been known and published 

 for a number of years, it does not seem to have met with general 

 acceptance. Man}' persons, indeed, with whom I have spoken 

 do not seem to know of it at all, and for that reason I do not 

 think it amiss to give an account of it here. 



I have had the pleasure of working under Professor C. Semper, 

 the discoverer of this method, for two years, and have seen, as 

 well as prepared, many specimens. I have seen some specimens 

 that have been prepared b}-^ this method over ten years ago, and 

 not the slightest change has taken place in them, and they look 

 as beautiful as those just finished. 



The method requires close attention at certain stages, and the 

 result depends upon the amount of care bestowed ; the end, when 

 successful, fully repays any amount of care that has been taken. 



Nearly any animal or animal tissue may be prepared by this 

 method ; some require naturally more care than others — 'Of fish, 

 where there is a large quantity of fatty substance present, the 

 greatest care is to be taken. 



Dissections of animals are especially adapted for this method, 

 and most of Prof. Semper's preparations are in this form. If 

 desirable, when finished, the different systems of organs may be 

 colored and thus serve as beautiful specimens for demonstration. 



The object to be prepared is first placed in a solution of 

 chromic acid of about ^ to ^ per cent., or even 1 per cent. 

 In the case of dissections, these are to be prepared after the 

 animal is killed and then placed in a dissecting tray, the bottom 

 of which is filled with wax, so that diff"erent parts may be pinned 

 out and thus better exposed to view ; the tray may be then filled 

 with the chromic acid solution. 



The size and consistency of the object determines the length 

 of time that it should remain in the solution ; Annelides, small 

 Gastropoda or Lamellibranchiata, small organs, as kidneys, etc., 

 or small vertebrates, as frogs, mice, birds, etc., should remain in 

 from six to eight hours ; larger animals or organs from eight to 

 twenty-four. 



The chromic acid is merely to kill the tissues, and at the same 



