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 formulae 



R 4- o, R -|-2o, R 4" ^ o, 



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 

 coniferae appear well characterized by the presence of the 

 hydrocarbon c^h^ and its oxides ; but the same composition 

 is found prevailing among the aurantias, 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 formulae 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 



i2 



