A^t;ain if one molecule of isobutyric acid could bo combined with three 

 molecules of acetic acid, the whole of the oxygen atoms being eliminated, the 

 molecule of hexahydrocymcne could be arranged, the migration of one hydrogen 

 atom in the methyl group of two acetic acid nioleculrs Ix-ing necessary for valency 

 purposes. The carbon and hxdrogen atoms thus derived from the three acetic 

 acid molecules represent 60 per cent, of the whole in the above arrangement, 

 those of butyric acid 40 per cent. The free acids occurring in the latex of A. 

 Cininingliiinii were found to be butyric and acetic, and the percentage of barium- 

 acetate in the barium salt obtained from thes-? acids was 60-38 per cent.; that 

 of the barium but\rate being 39*62 per cent. The somewhat close agreement 

 between the theoretical requirements for these acids in the arrangement suggested 

 above for a C,,, H.,,, hydrocarbon of this series, and the amount of each acid actually 

 present in the latex, appears to be a remarkable coincidence. 



The formation of these acids goes on continuously, and if these are not used 

 up in the constnictive metabolism of the plant, would ultimately become in excess, 

 if not otherwise removed or fixed. Liebig was of the opinion that some, at any 

 rate, of the organic acids were formed from carbon dioxide and water in the cells 

 of the plant (see letter on Chemistry, XVIII). The constituents required for 

 the completion of the compounds found in this latex appear to have been derived 

 more largely from below, as the upper portion of the tree had been removed previous 

 to the accumulation of the exudation, and as this was continuously forced up there 

 must have been sufficient material obtainable to assist in the metabolic process 

 of the plant. 



That some of the fatty acids do enter into the process of constructive meta- 

 bolism, being thus subjected to complete alteration, is generally accepted, and the 

 increase of carbohydrates, corresponding to the diminution in acidity in some 

 portions of the plant, is a case in point. 



That the changes which go on are continuous, is indicated by the fact of 

 the alteration of the unsaturated In clrocarbons into resinous products, even after 

 they had been obtained by steam distillation from the latex and kept in closed 

 bottles. It was this alteration that enabled the puicr saturated hydrocarbon, 

 C,„H„„ to be obtained, as this harl undergone no alteration during the time 

 necessary for the resinificati(;n of tlic unsaturated bodies; so that when distilled 

 directly the menthane was obtained practically })ure at the first distillation 



It thus apjK-ars that the lully saturated hydrocarbons are the lirst f(jinied 

 bodies of this group, and that the alteration by oxidation commences at once, 

 the more stable and less volatile >ulystances, as the tei-pnus and ihe'nsins, being 

 eventually formed. 



It might be suggested that the format nm ol some of tiie eonsfituents of the 

 latex might be due to the injury to whidi the trees had been subjected, and that, 



