MILK. 173 



In order to estimate as nearly as possible the number of 

 globules existing in the milk, M. Donne has invented an ap- 

 paratus which he has termed a lactoscope. By means of 

 this instrument the milk can be examined in very thin 

 layers, and in proportion to the opacity of the milk spread 

 out into such layers, so will be its richness, the deeper the 

 stratum the richer the milk. 



There is one fallacy attending the use of this instrument 

 which requires to be noticed : this, however, is one which has 

 reference to its employment in testing the quality of the 

 milk of the cow, the ass, and the goat, and not of the milk 

 of woman. 



The milk of commerce is frequently adulterated with sub- 

 stances such as chalk and flour, which are intended to 

 heighten its colour and opacity ; the presence of these then 

 in the milk would, to a certain extent, lessen the value of 

 the opinion to be deduced from an examination of the milk 

 with the lactoscope of Donne. 



The effect, however, of the admixture of chalk and flour in 

 heightening the opacity of milk is not so considerable as 

 might be supposed, and this is especially found to be the 

 case when it is spread out in thin layers as in the lactoscope. 

 Moreover, the presence of an insoluble substance in the milk 

 might be detected by means of the microscope. 



Applied to the examination of the milk of woman, the 

 lactoscope would not be subject to the above fallacy. 



Having now shown that the globules constitute an im- 

 portant element of the milk, and the methods by which their 

 number may be ascertained, we may, in the next place, de- 

 scribe more particularly the qualities of good milk. 



Healthy milk may be defined to be an alkaline fluid, 

 having a specific gravity of about 1-032, holding in suspen- 

 sion numerous perfectly spherical and discrete globules, 

 soluble 'in ether, and therefore of a fatty nature, and in 

 solution cheese and sugar, together with various salts. 



If, on the contrary, the milk be viscous pr acid, if the glo- 

 bules be ill formed or few in number, if they adhere together 

 in masses and do not roll freely and separately in the serum, 



p 3 



