372 



SECRETION. 



The human milk-globules measure from ^^ to T? Vir of an inch in diameter. They are 

 usually distinct from each other, but they may occasionally become collected into groups 



without indicating any thing abnormal. 



FIG. 103. Human milk-globules, from a healthy 

 n 

 .) 



lying-in woman, eight days after delivery. 

 (Funke.) 



In a perfectly normal condition of the glands, 

 when the lacteal secretion has become fully es- 

 tablished, the milk contains nothing but a clear 

 fluid with these globules in suspension. The 

 proportion of fatty matter in the milk is from 

 twenty-five to forty-eight parts per thousand, 

 and this gives an idea of the proportion of 

 globules which are seen on microscopical ex- 

 amination. 



There has been a great deal of discussion 

 with regard to the anatomical constitution of 

 the milk-globules. In many late works it is 

 stated that these are true anatomical elements, 

 composed of fatty matters surrounded by an 

 albuminoid membrane ; but some writers as- 

 sume that the fat is merely in the form of an 

 emulsion and is simply divided into globules 

 and held in suspension, like the fatty particles 

 of the chyle. No one, however, has assumed 

 to have seen the investing membrane of the milk-globules, and its existence is only 

 inferred from the behavior of these little particles in the presence of certain reagents. 

 It is unnecessary to review in detail the numerous opinions that have been advanced 

 on this subject. As far as can be ascertained by simple examination, even with the 

 highest magnifying powers, the globules appear perfectly homogeneous ; and the burden 

 of proof rests with those who profess to be able to demonstrate the existence of an 

 investing membrane. Robin, one of the highest authorities on these subjects, argues 

 against the existence of a membrane and opposes the observations of those who assume 

 to have demonstrated it, by explanations of the phenomena produced by reagents, which 

 do not involve, as a necessity, the presence of such a structure. The arguments in favor 

 of its existence are not very satisfactory ; and the experiments upon which they are 

 based relate chiefly to the action of ether upon the globules before and after the action 

 of other reagents. 



If a quantity of milk be shaken up with an equal volume of ether, the mixture 

 remains opaque ; but, if a little potash be added, the fatty matters are dissolved, and the 

 mixture then becomes more or less clear. These facts are all that can be observed with- 

 out following out the changes with the microscope. Robin has shown that the fatty 

 particles are acted upon when the milk is thoroughly agitated with ether alone ; and 

 that the opacity is then due to the fact that the ether, with the fat in solution, is itself 

 in the form of an emulsion. If the opaque mixture of milk and ether be examined 

 with the microscope, globules are seen, larger than the ordinary milk-globules, paler, 

 and possessing much less refractive power. These he supposes to be composed of fat 

 and ether. If potash be added, either before or after the addition of ether, the consti- 

 tution of the whole mass of liquid is changed, and it becomes somewhat transparent, 

 though by no means perfectly clear. It is assumed that, in the first instance, the ether 

 does not attack the globules, because it has no effect upon the membrane which is sup- 

 posed to exist, and that the potash acts npon the membrane, allowing the ether then to 

 take up the fat ; but, if the observations of Robin be correct, it is evident that this view 

 cannot be sustained. 



If dilute acetic acid be added to a specimen of milk under the microscope, the glob- 

 ules become deformed, and some of them show a tendency to run together; an appear- 

 ance which is supposed by Henle, who was the first to study closely the action of acetic 



