THE CHEMISTRY OF THE FATS
Thc chief cliaraotcristic constitucnts of nll fatty siibstunccs arc the fntty acids. Throughout nuture all the cvcn numbered straight c h i n siiturutcd fatty acids from C, to C2, and crcn liiglicr arc lilio~li to cxist along with scvcral of the corrcsponding uiisaturntcd compounds. By far the most common saturated acids arc palmitic (Clo) and stcnric (CIS), while the unsaturated member occurring in greatcut; nbundance almost universally in fats is oleic ncid which contains 18 carbon n t o m and 1 double bond in the 9 : 10 position. This 9 :lo position appears to be of considcrnblc importiijicc in naturc for it is well established that in tho vast mirjority of unsaturated acids, onc double bond is to bc found in this part of tlie molcculc. A theory to account for the importancc of this position in the molccule still rciuains to be found. It should bc remembered, too, that from a biological point of view, thc insertiou of n double bond has a t least two main results. In the first plncc it rcndcrs the compound less stablc and thcreforc possibly ciiuscs it to be inore readily oxidized, a i d in thc second place it greatly lowcrs the mclting point of the compound. . For csamplc, olcic acid is much more rcadily oxidized than stcaric ncid in vitro and tlic latter melts crt 70" wlierens olcic is still liquid \vcll below roonu toiiipi5raturc.
Tiino is not iivailable tonight for speaking of the dil'fcrcnccs bctwccii the cl~arnctcristic fatty acids in thc