CIRCUMSTANCES AFFECTING COMPOSITION OF MILK. 977 



immediate coagulation. The quantity of acid necessary to produce coagu- 

 lation sufficiently rapid to be immediately visible, will vary with the amount 

 of casein present in the particular specimen of milk, 5 drops in some instances 

 producing a coagulation as rapid as that produced by 10 drops in others. 

 In no specimen did Mr. Moore fail to produce coagulation by adding a suffi- 

 ciency of acid. Acetic acid without heat produces in Human milk a slow 

 separation of soft flaky coagula; but when heat is employed, a more perfect 

 coagulation is produced by small, than by large quantities of this acid. 

 Rennet does not seem to act upon the casein of Human milk, unless an acid 

 be also present. In several of these particulars, as well as in its small pro- 

 portional amount, the Casein of Ass's milk bears a closer resemblance to 

 that of Human milk than does that of the Cow. The Sugar of Milk, which 

 may be obtained by evaporating whey to the consistence of a syrup, and 

 then setting it aside to crystallize, forms four-sided prisms, whose compo- 

 sition is C24,H19,O19 + 5HO. In many of its properties it bears a 

 close resemblance to Glucose or Grape sugar, into which it is readily con- 

 verted by the agency of dilute sulphuric or hydrochloric acid, or by the 

 acetic or citric acids. It is readily made to pass into the lactic and butyric 

 fermentation, by the appropi'iate femeuts; but is with difficulty brought to 

 undergo the vinous fermentation. The Saline matter contained in milk, ap- 

 pears to be nearly identical with that of the blood ; with a larger proportion 

 of the phosphates of lime and magnesia, which amount to 2 or 2J parts in 

 1000. These phosphates are held in solution chiefly by the casein, which 

 seems to have a power of combining with them even greater than that of albu- 

 men : the presence of a minute proportion of free alkali also assists their solu- 

 tion. A small portion of iron in the state of phosphate, together with the 

 chlorides of potassium and sodium, may also be detected in milk. 1 



814. The proportion of these different constituents is liable to great vari- 

 ation, from several causes. Thus, the whole amount of the solid constit- 

 uents may vary from 86 to 138.6 parts in 1000; the difference being partly 

 due to iuvidual constitution, but in great part also to the amount and char- 

 acter of the iugesta. The average seems to be between 100 and 120 parts. 

 The following table 2 will serve to indicate the usual composition, as well as 

 the ordinary variations occurring in Human milk: 



Joly Henry 



and Bodecker. Griffith. Doyere. Simon. and Brunner. 4 



Filhol. 3 Chevallier. 



Water, 874.6 882.2 875.00 873.8 861.8914.0 879.5 900 



Siiuar of Milk, .... 68 64.6 61 76 70.0 39.2 62.4 65.0 62.0 



Fat 47.5 31.0 25.41 38.8 8.0 54.0 35.5 17.3 



All. umen, Casein, etc., . 9.8 19.0 12.fi8 16.4 19.645.0 15.2 6.3 



Salts, 11 3.3 1.55 1.8 1.6 2.7 4.5 14.0 



Schukowsky 5 gives 30 per 100 as the average proportion of oleaginous mat- 

 ters in the milk of Russian women. Milk contains about 3 per cent, of 

 its volume of Gas, having a percentage composition of 55.15 of Carbonic 

 acid, 40.56 of Nitrogen, and 4.29 of Oxygen. It further appears from the 

 analyses of Simon, that the proportion of the different ingredients is liable 

 to variation according to the time which has elapsed since parturition. The 

 quantity of Casein is at its minimum at the commencement of lactation, 

 and then gradually rises until it attains a nearly fixed proportion. The 



1 Hiiidlen in Annalen cler Chemie uncl Pharmacie, Bd. xlv, p. H;:J. 



2 Canstatt's Jahresbericht, 1860. 3 Henle and Mui.-sner's Bericht, 1857, p. 329. 



4 Brunner, Pfluger's Archiv, Bd. vii, 1873, p. 4'21. 



5 Pfliiger's Archiv, 1874, Bd. viii, p. 597. See also Lowit for a comparison of the 

 results obtained by analyzing milk in the several ways recommended by Trommer, 

 Hnppe-Seyler, and" Schukowsky, in Pfluger's Archiv, 1874, Bd. ix, p. 65. 



