HUMAN MILK. 



127 



Under the influence of extracts of the pancreas, the caseinogen, 

 before it is clotted by the milk-curdling ferment of the gland, passes 

 through a stage in which it coagulates by heat. This was termed 

 the " metacasein " reaction by its discoverer, Sir William Eoberts. 1 It 

 does not appear to be due to the simultaneous development of acid 

 produced by the fat-splitting ferment of the pancreas, but rather to 

 the action of trypsin. Edkins 2 showed that Klihne's purified trypsin 

 also produces " metacasein " in an early stage of its action, though it 

 does not produce coagulation of milk. 



The composition of milk varies in different animals; human milk 

 and cows' milk are those which have been most investigated. There 

 are also variations due to constitution, state of nutrition, and age. 



Human milk. The mammary glands of new-born animals of both 

 sexes often secrete a small quantity of milk for a few days. It is 

 popularly termed " witches milk!' It is alkaline. 3 Analyses by Schloss- 

 berger and Hauff, 4 Gubler and Quevenne, 5 and Genser, 8 show that the 

 milk of new-born children contains from 1'05 to 2'8 proteicl, O82 to 

 146 fat, 0'9 to 64 sugar, and 0'8 salts per cent. 



Colostrum. This liquid is yellower and more alkaline than fully- 

 formed milk. It contains colostrum corpuscles, rather more solids than 

 milk, and coagulates on heating. It contains little or no caseinogen, 

 but a mixture of lacto-globulin and lactalbumin. 7 The globulin is only 

 present in traces in fully-formed milk. The following analyses are by 

 Clemm, 8 with the exception of the last, which is by Tidy. 9 



1 Proc. Roy. Soc. London, 1879, 1891. 



" Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 203. 



3 Witches' milk obtained from foals by Ammoii (Jahrcsb. u. d. Fortschr. d. Thier-Chem., 

 "Wiesbaden, 1876, S. 118) was acid, but this was probably due to fermentation having set in. 



4 Ann. d. Chem., Leipzig, Bd. xcvi. S. 68. 



5 Gaz. med. de Paris, 1856, p. 15. 



6 Jahrb.f. Kindcrh., Leipzig, N. F., Bd. ix. S. 60. 



7 J. Sebelien, Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 135. 



8 Wagner's " Haudworterbuch d. Physiol,." Bd. ii. S. 464. 



9 Lond. Hosp. Rep., 1867-8, p. 77. See also Woodward (Journ, Exper. Med., Baltimore, 

 1897, vol. ii. p. 217), for recent analyses of human colostrum. Colostrum corpuscles are 

 not constantly present. 



