83 



ture through the opaque spot with a curved needle, which 

 serves to fix the eye. Another needle is then passed at 

 right angles to the former, and armed with a very fine liga- 

 ture, which is allowed to remain loose. The first liga- 

 ture being then strained, an incision is made equal in 

 length to the nebulous portion ; then raising it by the ligature, 

 the whole opaque portion may be removed with a sharp 

 curved scissors, and by drawing the ligature of reserve, the 

 two fresh incised surfaces brought together. 



Professor Kane read a paper " on the Composition of 

 certain essential Oils." 



The first object of the author, in commencing the exami- 

 nation of this subject, was to collect facts towards an ap- 

 proximate solution of the problem, " whether there can be 

 found any law connecting the composition of the secretions of 

 plants of the same genus or natural family." The three 

 alcaloids of the genus cinchona, giving the formulas 

 r + o, R 4-2o, R + So, 



appear to furnish a glaring instance of the existence of such 

 a law ; but the want of connexion in the composition of the 

 constituents of opium might be advanced in opposition, 

 although not quite a parallel case. The family of the 

 coniferas appear well characterized by the presence of the 

 hydrocarbon c 5 h 4 and its oxides ; but the same composition 

 is found prevailing among the aurantiae, as in oil of lemons, 

 — the myrti, as in the neutral oil of cloves, — and the lauri, 

 as in common camphor ; whilst other members of the same 

 family, as oil of cinnamon, have formulas altogether dif- 

 ferent. 



The members of the family of the labiatae are characte- 

 rized by yielding remarkably aromatic oils by distillation ; 

 and as many of these oils, from their use in medicine, are 



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