MICROSCOPIC DRAWING AND ENGRAVING. 



That eminent physiologist transfused milk into the blood vessels 

 of various animals, with all the precautions necessary to prevent 

 the admission of air. It was found generally that the vital 

 functions of the animal, were neither interrupted nor disturbed ; 

 the milk mingled with the blood and circulated with it through 

 the system, its presence being detected in all the vessels. But the 

 most interesting and important result of these researches, was, 

 that the butter globules of the milk were found to assimilate 

 themselves to, and play the same part with, the white globules of 

 the blood, and like them were gradually converted into red cor- 

 puscles, and it appeared that the place where this change was 

 elaborated was, as in the case of the white corpuscles of the 

 blood, the spleen. 



These researches and their results, however, being recent and 

 novel, must be received with that caution which is always neces- 

 sary in physical researches, until they are repeated and like results 

 reproduced by other observers. 



93. The question of the quality of milk in respect to its 

 richness, has high sanitary and economic importance, and yet it 

 is one which hitherto does not appear to have received the atten- 

 tion which it merits. "We hear on all hands the adulteration of 

 milk complained of, and the frauds of the milkman reprehended ; 

 but we seldom hear of any practical methods applied for the pur- 

 pose of detecting and checking this abuse. It will perhaps not 

 be out of place here, to say a few words in illustration of this 

 question. 



94. The richness of milk, as has been just observed, depends on 

 the proportion of butter globules which it contains ; these globules 

 being lighter, bulk for bulk, than the liquid in which they float, 

 have a tendency to rise to the surface, and when milk is allowed 

 to stand still they do rise to the surface, where, mixed with a 

 certain portion of the cheesy principle and sugar-of-milk, they 

 form cream. Now it follows, that being thus lighter, bulk for 

 bulk, than the fluid in which they float, they have a tendency, 

 when mixed with that fluid, as they are when the milk is in its 

 natural state, to render the milk lighter, and the larger the pro- 

 portion is in which these butter globules are mixed with the milk, 

 the lighter will be the milk. It was therefore inferred, that the 

 lightness of the milk might be taken as a test of its richness, and 

 M. Quevenne invented a species of hydrometer, which he pro- 

 posed to apply to test the richness of milk, in the same manner 

 as the ordinary hydrometer is applied to test the strength of 

 spirits. But the indications of this instrument, ingenious as it is, 

 are fallacious. 



95. Let us suppose that the fraudulent milkman allowing the 

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