1026 OF GENERATION. 



1027. It is very interesting to observe that Milk contains the three classes of 

 principles which are required for human food the Albuminous, the Oleaginous, 

 and the Saccharine ; and it is the only secreted fluid in which these all exist to any 

 considerable amount. It is, therefore, the food most perfectly adapted for the 

 young animal ; and is the only single article supplied by nature in which such 

 a combination exists. Our artificial combinations will be suitable to replace it, 

 just in proportion as they imitate its character; but in none of them can we 

 advantageously dispense with milk, under some form or other. It should be 

 remembered that the Saline ingredients of milk, especially the phosphates of 

 lime, magnesia, and iron, have a very important function in the nutrition of the 

 infant, affording the material for the consolidation of its bones and for the pro- 

 duction of its red blood-corpuscles ; and any fluid substituted for milk, which 

 does not contain these, is deficient in essential constituents. It is very justly 

 remarked by Dr. Rees, 1 that, of all the secreted fluids, Milk is most nearly allied 

 in its composition to Blood. 



1028. The proportion of the different ingredients in the Milk of different 

 animals, is subject to considerable variation ; and this fact is of much practical 

 importance in guiding our selection, when good Human milk cannot be con- 

 veniently obtained for the nourishment of an infant. The first point to be in- 

 quired into, is the quantity of solid matter contained in each kind ; this may be 

 determined either by evaporation, or by the specific gravity of the fluid. The 

 Specific Gravity of Human milk is stated by Dr. Rees (loc. cit.) to vary between 

 1030 and 1035 ; others, however, have estimated it much lower. That of the 

 Cow appears to be usually about the same; that of the cream, however, being 

 1024, and that of the skimmed milk about 1035. The variation will in part 

 depend (as in the case of the urine) upon the quantity of fluid ingested, and in 

 part, it is probable, upon the manner in which the milk is drawn ; for it is well 

 known to milkers, that the last milk they obtain is much richer than that with 

 which the udder is distended at the commencement. The quantity of solid 

 matter obtainable from Human and from Cow's Milk by evaporation, seems, like 

 the specific gravities of the fluids, to be nearly the same. In the relative pro- 

 portion of the ingredients, however, there is a considerable difference ; there 

 being much more sugar and less casein in Human Milk, than in that of the Cow. 

 The following table exhibits the relative proportions of the different ingredients, 

 in the Milk of various animals, from which that fluid is commonly obtained : 



Cow. Goat. Sheep. Ass. Mare. 



Water 861.0 868.0 856.2 907.0 896.3 



Butter 



Casein ...... 



Sugar of Milk and extractive matters 

 Fixed salts 



38.0 33.2 42.0 12.10 traces 



68.0 40.2 45.0 16.74 16.2 



29.0 52.8 50.0 \ 



6.1 5.8 6.8 / 



62.31 87.5 



It appears from this, that, whilst the milks of the Cow, G-oat, and Sheep do not 

 differ from each other in any very prominent degree, that of the Ass and Mare 

 is a fluid of very dissimilar character, containing a comparatively small propor- 

 tion of casein, and scarcely any butter, but abounding in sugar. Hence it is, 

 that it is much more disposed to ferment than other milk; indeed the sugar of 

 mare's milk is so abundant, that the Tartars prepare from it a spirituous liquor, 

 to which they give the name of koumiss. It would further appear that no milk 

 more nearly approaches that of the Human female, in the proportion of its 

 ingredients, than that of the Sheep and Groat; these both possess, however, a 



between each birth, and the children were permitted to take the breast until they were 

 running about at play. At the time when Dr. G. wrote, she had been nine years a widow, 

 and was obliged to have her breasts drawn daily, the secretion of milk being so copious. 

 1 "Cyclopcedia of Anatomy and Physiology," Art. "Milk." 



