786 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



et al. i37 presented the following analysis: free fatty acids, 29%; combined 

 fatty acids (as glycerides, waxes, and esters), 36%; and unsaponifiable 

 fraction, 32%. In a later study, 438 the unsaponifiable fraction was found 

 to contain 30 to 46% of hydrocarbons, 14 to 19% of cholesterol, and 20% 

 of aliphatic alcohols, and also other unidentified products. The hydro- 

 carbon fraction contained 30 to 40% of squalene and possibly pentacosane. 

 No vitamin A, carotene, vitamin K, or provitamins D 2 and D 3 could be 

 detected, by chemical tests, in the sebum or in the separated fractions. 

 However, appreciable amounts of vitamin E were believed to be present 

 in a concentration of 20 milligram per cent. 



Pritchard and associates 439 obtained samples of skin lipids from human 

 subjects by the use of an apparatus consisting of a filter paper attached 

 to sponge rubber pads fastened to plungers and operated by compressed 

 gas. This device enabled them to obtain all available lipids from a speci- 

 fied area of the skin. The over-all range of values for the forehead samples 

 varied between 0.05 and 0.50 mg./sq. cm., with a mean value of 0.19 mg. 

 for men, and 0.17 mg. for women. 



Cerumen is produced in increased amounts in hamsters on a fat-free diet. 

 Christensen and Dam 440 noted that the membrani tympani were covered 

 by a thick layer of a light yellow secretion, which proved to be cerumen. 

 In some cases there was sufficient secretion to plug the external ear canal 

 completely. This secretion did not occur in the case of hamsters fed 10% 

 of lard or of those animals which received a supplement of linoleic acid 

 (up to 28 mg. daily). It is therefore postulated that the abnormal secre- 

 tion of cerumen is probably due to a deficiency of essential fatty acids in the 

 diet. 



Weitzel and Lennert 441 reported on the composition of the secretion 

 of the preen gland of ducks. When this secretion is spread over the feath- 

 ers, it produces the hydrophobic effect which prevents the feathers from 

 becoming wet; in this manner it assists in affording buoyancy in the case 

 of aquatic birds. The nonsaponifiable fraction, which was composed en- 

 tirely of octadecyl alcohol, constituted about 50% of the total lipid. The 

 balance of the lipids in the secretion were fatty acids. Of these, 36% were 



437 R. M. B. MacKenna, V. R. Wheatley, and A. Wormall, /. Investigative Dermatol., 

 15,33-47 (1950). 



438 R. M. B. MacKenna, V. R. Wheatley, and A. Wormall, Biochem. J., 52, 161-167 

 (1952). 



439 J. E. Pritchard, L. D. Edwards, and J. E. Christian, /. Am. Pharm. Assoc., 88. 

 546-549 (1949). 



440 F. Christensen and H. Dam, Acta Physiol. Scand., 27, 204-205 (1952). 



441 G. Weitzel and K. Lennert, Z. physiol. Chem., 288, 251-265 (1951). 



