428 ORIGIN OF MILK FAT 



foreign to the birds ' economy may, just as in milk, pass into 

 the secretion of the coccygeal gland. 79 



Haptogenic Membranes. In conclusion a few words may 

 be devoted to the old question as to the form in which the 

 fat exists in milk and the nature of the much discussed 

 haptogenic membranes which surround the fat globules. 

 The contention on this subject took its inception in the 

 observations of Ascherson in 1840 ; and it is not settled to- 

 day. The physicist Quincke took the position that the cover- 

 ing of the fat globules consisted merely of a layer of protein 

 condensed about the globules by surface tension ; V. Storch 

 and a number of other observers (as, recently, W. Voltz 80 

 and H. Bauer 81 ) held that the haptogenic membrane is of a 

 gelatinous, relatively firm character, often compared to the 

 stroma of red blood cells. Voltz refers with emphasis to the 

 fact that if milk globules passed through a column of water 

 are skimmed off from the surface of the water and centrif- 

 ugated, invariably in a short time the coverings of the milk 

 globules are largely precipitated and collect as a firm (not a 

 gelatinous) substance at the bottom. When the fat is re- 

 moved by use of a Soxhlet apparatus the haptogenic mem- 

 branes remain behind. Under the microscope the isolated 

 coverings show very irregular appearances. Analysis and 

 hydrolysis (a few decigrams may be obtained from a liter 

 of milk) show that they contain a very large proportion of 

 ash along with protein, and consist not only of casein but also 

 of calcium salts of the fatty acids. 82 All this does not in the 

 author's opinion prove that they are organized, preformed 

 structures in the milk. It may easily be fancied that a layer 



F. Rohmann (Breslau), Hofmeister's Beitr., 5, 110, 1904. 



80 W. Voltz (Zootech. Instit., Agric. High School, Berlin), Pfliiger's Arch., 

 102, 373, 1904; Handb. d. Biochem., 3', 394, 1910. 



81 H.. Bauer (Instit. of Dairying, Agric. High School, Vienna), Biochem. 

 Zeitschr., 32, 362, 1911. 



82 E. Abderhalden, and W. Voltz, Zeitschr. f. physiol. Chem., 59, 13, 1909; 

 Bredenberg (N. Zuntz's Lab.), Abhandl. d. Agrikulturwissenschaftl. Ges. in 



'Finnland, H. 4, Helsingfors, 1912, cited in Centralbl. f. d. ges. Biol., 1912, 

 No. 2011. 



