J814.] On the Uses of the Dorsal Vessel. 355 



recently considered die dorsal vessel as a vestige of a heart, or as a 

 viscus which does not perform any of the functions of that organ. 

 Before an organ ceases to exist it no longer performs the functions 

 which it performed in those animals where its presence is absolutely 

 necessary. He mentions, as an instance of this cessation of functions 

 before the organ disappears, the hands, which still exist in a great 

 number of species, though they are no longer of any utility as 

 hands. 



From the statement which we have now made it is evident that 

 the non-existence of ramifications of the dorsal vessel has been 

 admitted by the greater number of anatomists. But as doubts still 

 exist on the subject, because some observers describe these ramifi- 

 cations with details which appear the result of the most attentive 

 examination, we have thought it worth while to undertake the 

 researches, of which we shall now give an account. 



(To lie continued.) 



Article VI. 



Experiments to determine the Quantity of Oxygen in the Oxides of 

 Cerium. By W. Hisinger.* 



As all the attempts hitherto made to reduce the oxide of cerium 

 to the metallic state have failed of success, chemists cannot deter- 

 mine the quantity of oxygen which the oxides of that metal contain 

 by direct solution of it in acids. I have therefore had recourse to 

 the method pointed out by Berzelius in his dissertations on the 

 chemical proportions in which bodies unite ; namely, to determine 

 the proportion of oxygen in the bases by the quantity of that prin- 

 ciple contained in the weight of acid with which a given portion of 

 these bases unites. 



Pure muriatic acid was saturated by long boiling with oxide of 

 cerium carefully purified. The greatest part of the oxide was dis- 

 solved in the acid. The solution was boiled down to dryness, in 

 order to decompose all the insoluble salt which it contained. It was 

 then dissolved in water, and by that means separated from the 

 superabundant oxide. Nitrate of silver was dropped into the solu- 

 tion as long as any precipitate fell. The precipitate was separated 

 by means of a filter carefully weighed. It was washed, and melted 

 by the heat of a lamp, in a small glass capsule. Its weight, reckon- 

 ing 0-01S gramme (0*278 grain), which remained on the filter, 

 amounted to 1'819 gramme 28*09 grain) , 



The solution was diluted with water, and freed from silver by 

 [)8 of muriatic acid. The oxide of cerium was then precipitated 



• Translated (turn the Koni;'. Vctcnskap, Academical Handlingar. Part II . 



fei wis. 



/ '1 



