MILK. 157 



" are nothing else than the curled membranes of the globules, 

 the contents of which, the butter, constituting the long 

 streaks : we may easily convince ourselves of this by adding 

 a little water. The streaks disappear, and we see in their 

 place oleaginous drops of different forms, while the little 

 membranes remain either attached to the glass or indiffer- 

 ently curved, swimming in the serum. These membranes 

 are insoluble in ether, which dissolves the drops." 



These observations of Mandl, presuming for a moment 

 that they are accurate in every particular, are yet insufficient 

 to prove the existence of a distinct membrane surrounding 

 the globules, although they certainly would be so, if correct, 

 to establish the fact that they are constituted of two different 

 substances, the one of which is soluble in ether and the other 

 insoluble. Had iodine been employed, and had it been im- 

 bibed by the supposed membrane, and turned of a deep brown, 

 the reality of the existence of the membrane in question 

 might have been considered as demonstrated : but we know 

 that iodine does not affect the colour of the milk globule in 

 the least. 



I am far, however, from attaching the smallest importance 

 to the experiment of Mandl, because I conceive that he has 

 misinterpreted the appearances which he noticed. The 

 larger streaks are not constituted of a single elongated glo- 

 bule, but are made up by the union of several milk globules, 

 as is evident, first, from the size of the streaks, and, second, 

 from the traces which they bear of such a composition in 

 themselves ; as, for example, the occurrence of contractions at 

 certain intervals, while the smaller lines, and which are most 

 generally absent, are formed usually by other globules of 

 less size joining at an angle the larger streaks. The so- 

 lubility of the one in ether and the insolubility of the other 

 in that re-agent, I have not been able to observe. 



The opinion of Henle that the milk globule is furnished 

 with an envelope rests chiefly upon the manner in which 

 acetic acid acts upon it. 



Henle thus describes the effects of the application of acetic 

 acid : 



o 3 



