SEBACEOUS GLANDS AND COCCYGEAL GLAND 427 

 as protein derivatives (from the branched chain of leucin, 

 H CH 2 CH.NHz COOH). 78 In the author 's opinion the oc- 



currence of the normal acids, C 4 , C 6 , C 8 , C 10 , C 12 , C 14 , in 

 the milk is very suggestive of the possibility that they may 

 be due to an oxidation reduction from the typical higher 

 fatty acids, the long chain of the latter being gradually short- 

 ened, each time by two carbon atoms by oxidation at the 

 /^-position, following Knoop's idea (vide supra, p. 392) : 



Old.2 C-/X12 



CH 2 > CH 2 > CH 2 > CH.OH > COOH. 



CH 2 CH 2 CH 2 CH 2 



CH 2 CH.OH COOH COOH 



CH 2 CH 2 



COOH COOH 



Sebaceous Glands and Coccygeal Gland. In attempting 

 to understand the function of the mammary glands the idea 

 that they are really modified sebaceous glands is not without 

 significance. A number of the lower mammals (as the 

 monotremes) have instead of the mammary glands a large 

 number of small dermal glands and the offspring lick the 

 surface of the abdomen instead of sucking. It is interesting, 

 too, to know that in the material secreted by ordinary 

 sebaceous glands casein has been recognized. 



The coccygeal gland of water fowl corresponds, too, in its 

 development, structure and function, to a modified sebaceous 

 gland. Its fatty secretion, however, according to Rohmann, 

 is not ordinary neutral fat, but consists for the most part of 

 esters, combinations of fatty acids with octadecylalcohol 

 (derived by oxidation from oleic acid and stearic acid) . Fats 



78 Literature upon The Occurrence of Fatty Acids in the Body : W. Glikin, 

 H'andb. d. Biochem., 1, 95-102, 1909. 



