346 MILK. 



by Donne,* which consists of two tubes that may be pushed 

 into one another by means of a fine screw, each tube being closed 

 at the opposite extremities by a plane of glass. The determination 

 is made by ascertaining the thickness of the milk-stratum, through 

 which the light of a taper may be detected ; the opacity of the 

 milk being usually regarded as a test of the quantity of fat con- 

 tained in it. Areometric determinations, such as Jones, Chevallier 

 and Henry, as well as Quevenne, have proposed for the determina- 

 tion of the density, and consequently of the goodness, of the milk, 

 frequently fail in their object, while Simon's suggestion of employ- 

 ing a solution of tannic acid, of known strength, which precipitates 

 butter and casein from the milk, may in many cases be open to 

 deceptions. Moreover, Lamperierre'st method of comparing the 

 density of fresh milk with that of milk which has been filtered 

 through paper, does not meet all the requirements of the case. 



We are still very deficient in accurate determinations of the 

 quantity of this secretion in women, but it must necessarily differ 

 in accordance with the various relations of nutrition in the female 

 while suckling. In women, the bodily constitution, the nature of 

 the food, external relations, temperament, &c., must obviously 

 influence the quantity as well as the composition of the milk. 

 The quantity of the milk is, moreover, dependent upon its con- 

 sumption, for in the early period of lactation, less milk is drawn 

 from the breasts than subsequently, when the infant requires a 

 larger amount of nutriment. Lamperierre determined, by means 

 of the apparatus described in p. 333, the quantity of milk secreted 

 in definite times by a large number of women, and found, as a 

 mean for each breast between 50 and 60 grammes in the course 

 of two hours If we were to assume that the secretion of milk 

 proceeds at an equal rate during the twenty-four hours, then 

 (taking 55 grammes as the mean) a woman might discharge 1320 

 grammes of milk in twenty-four hours from both breasts ; accord- 

 ing to this view, and assuming the mean weight of the female body 

 to be 60 kilogrammes, there would be secreted every twenty-four 

 hours during the period of lactation 22 grammes of milk for every 

 1000 grammes of weight. 



We may calculate with tolerable accuracy the quantity of milk 

 secreted by milch cows : according to the experiences of agricul- 

 turists, which coincide pretty closely with the results which 

 Boussingault obtained in his experiments on the effects of different 



* Compt. rend. T. 17, p. 588592. 

 t Op. cit. 



