MICROSCOPIC DRAWING AND ENGRAVING. 



in the case of the blood, that very similar appearances are pre- 

 sented, A multitude of minute pearly spherules with the most 

 perfect outline, reflecting light brilliantly from their centre and 

 varying in magnitude from the 12500th to the 3000th part of an 

 inch in diameter, and even larger still, are seen floating in the fluid. 

 The general magnitude and number of these globules vary 

 much, not only in the case of one species of animal compared with 

 another, but with different individuals of the same species, and 

 even with the same individual under different circumstances. 



87. In fig. 40, p. 97, we have given the appearance presented by a 

 thin disc, the 120th of an inch in diameter, of common cow's 

 milk magnified 400 times in its linear, and therefore 160000 times 

 in its superficial dimensions, engraved from a daguerreotype by 

 MM. Donne and Foucault. 



88. It appears from the researches of physiologists on this 

 subject that the pearl-like globules, which thus float in such 

 multitudes in milk are the constituents out of which butter is 

 formed. The serous fluid in which they float is composed of the 

 constituent out of which cheese is formed, combined with another 

 substance called sugar-of-milk, and water, the last constituting 

 from 80 to 90 per cent, of the whole, so that, in fine, milk in 

 general may be regarded as water holding in solution the sub- 

 stances called sugar-of-milk and caseine, the name given to the 

 cheesy principle, with the globules of butter already described 

 floating in it. 



89. The proportion in which these constituents enter into the 

 composition of milk varies, the richness always depending on the 

 proportion of globules of butter contained in it. 



90. The following is an analysis of the milk of the woman, 

 the cow, the goat, and the ass, according to Meggenhofen, Yan- 

 Stiptrian, Liuscius, Bonpt, and Peligot : 



Woman. Cow. Goat. Ass. 



Butter . . . .8-97 2-68 4-56 1-29 



Sugar of Milk . . . 1'20 5*68 912 6'29 



Cheesy matter . . . 1'93 8 '95 4 '38 1'95 



Water 87 '90 .82-69 81 '94 90-47 



100-00 100-00 100-00 100-00 



91. From this and similar analyses it appears that woman's 

 milk is by far the richest of the mammalia, containing generally 

 little short of 10 per cent, of butter, while the milk of other 

 species contains no more than from 1 to 4 per cent, of that 

 principle. 



It must, however, be observed that these are average proportions, 

 106 



