426 LIQUID PARTS OF ANIMALS. 



experiments on lactic acid, and pointed out its peculiar nature.* 

 He had also made experiments on curd, and pointed out its ana- 

 logy to albumen. Bouillon-Lagrange made a pretty minute exa- 

 mination of the properties of curd, and endeavoured to prove 

 that lactic acid is nothing else than acetic acid mixed with chlo- 

 ride of potassium, a little iron, and an animal matter. 



About the year 1805, Thenard published a paper on milk^ in 

 which he shows that butter may be separated from milk without 

 the access of air. He pointed out a mode of purifying butter by 

 fusion, and noticed some of its properties. Like Bouillon-La- 

 grange he considered lactic acid as merely acetic acid contami- 

 nated by animal matter. The same opinion had been advanced 

 by Fourcroy and Vauquelin.J 



In 1808, Berzelius published the second volume of his Animal 

 Chemistry. He analyzed cow's milk, and examined in detail 

 the properties of butter, curd, and whey. The constituents of 

 skimmed milk, according to his analysis, are, 

 Water, . . . ' . 92-875 



Curd (not free from butter), . . . 2-800 



Sugar of milk, . \ . 3 '500 



Lactic acid and lactate of potash, r , - *' 0-600 



Chloride of potassium, v .' . 0-170 



Phosphate of potash, ; . > *; >rif, 0-025 



Phosphate of lime and magnesia, with a trace of iron, 0-030 



100-000 



In 1830, an interesting paper was published by Braconnot on 

 casein, or the curd of milk, and on the new resources which it 

 opened to society. || He gives an account of the chemical pro- 

 perties of casein, and points out the various important uses to 

 which it may be applied. About the same time M. Macaire- 

 Princep made some experiments on the formation of butter.1" In 

 1832, Lassaigne published a number of analyses of the milk of 

 the cow before and after parturition ;** and in 1836 M. Peligot 

 gave a chemical analysis of the milk of the ass ;ff and in 1839 we 



* Scheele's Essays, p. 265. f Nicholson's Journ. xii. 218. 



J Mem. de Hnstitut, vi. 332. Djurkemie, ii. 409. 



|| Ann. de Chim. et de Phys. xliii. 337. 



If Bibliotheque Univer. xliii. 379, or Poggendorf s Annalen, xix. 48. 



** Ann. de Chim. et de Phys. xcix. 31. ft Ibid. Ixii. 432. 



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