[41] THE PRESERVATION OF MARINE ANIMALS HOVEY. 



One can easily inject the circulatory system of living- Salj)as with 

 Prussian blue by placing the point of a iine syringe in the slender 

 canal of the heart and operating it with a very gentle pressure. After 

 this the animals can be treated by the methods already detailed, and 

 the color will remain verj^ well after they have been put into alcohol. 



The Doliolids give good preparations when killed with the mixture 

 of sulphate of copper and sublimate, saturated sublimate alone, or 

 with the chrom-osmic mixture. After a few minutes wash the animals 

 thoroughly with fresh water and transfer them gradually to 70 per cent 

 alcohol. 



In general, fish present no difficulties in their preparation. If possi- 

 ble, they should be alive when put into the fixing fluid, because thus 

 only do they preserve the shape of the body well and keep the fins 

 completely distended. Those which have been dead for some time and 

 have been left to dry, having already lost much water, have the fins 

 contracted and dried, and when placed in alcohol they contract still 

 more. To preserve dead fish for anatomical purposes, inject them first 

 through the anus with 90 per cent alcohol and then put them into that 

 of 70 per cent. 



To prepare Amphiojcus with the mouth cirrhi distended, the animals 

 are allowed to die in sea water alcoholized to 10 per cent, and after 

 death, which usually occurs in a few minutes, they are transferred to 

 alcohol of 50 per cent, and gradually to that of 70 per cent. Miiller's 

 solution^ can also be used for killing, if suitable for the purpose for 

 which the animals are intended; but they remain colored, and often 

 swellings are formed in the sides of the body. Chromic acid of 1 per 

 cent is sometimes used for the killing. 



Oyclostomans, Selachians, and Ganoids. — Small specimens are put at 

 once into 70 per cent alcohol. With large specimens it is difficult for 

 the alcohol to penetrate the viscera, and it is necessary to make an 

 incision in the belly, or else to inject 90 per cent alcohol through the 

 anus repeatedly and at every change of fluid. 



Certain species of soft consistency, like Torpedo, are better fixed if 

 they are allowed to lie in 1 per cent chromic acid for a half hour before 

 they are put into alcohol. 



Embryos of Selachians (from 1 to 10 c. m. in length) are fixed in sat- 

 urated sublimate, where they may remain from five to fifteen minutes. 

 Be careful to wash well and to make use of the usual test with iodine. 

 When prepared thus they are also good for histological studies. Fair 

 success has attended the treatment of the embryos of Torpedo, with 

 the entire yolk sac attached, by placing them for fifteen minutes m a 

 mixture consisting of 1 per cent chromic acid and saturated sublimate 



1 Potassium bichromate, 2 grams ; sodium sulphate, 1 gram ; distilled water, 100 

 grams. 



2138— No. 39, Pt. M 4 



