THE CELLULAR CONTENT OF MILK 133 



minute clinical examination being made of a suspected cow than 

 would perhaps otherwise have been the case. A veterinary surgeon, 

 when called upon to examine a large herd of cows, would be assisted 

 by having his attention drawn to one or more suspected cows, and 

 would be able to devote more care to the examination of these 

 animals than he would be able to bestow on all the animals in the 

 herd. 



The nature of the cellular elements present in milk has been the 

 subject of much investigation both by histologists and by sani- 

 tarians. The histologist is concerned with the origin of the cells 

 in relation to the function of the gland. He wishes to know whether 

 the cells found in milk are derived from the gland itself or 

 whether they come from the blood and lymph. If they come from 

 the gland, the presence of a large number of cells in milk would 

 denote a very high degree of activity on the part of the gland tissue. 

 If, on the other hand, they come from the blood, it then becomes 

 a matter of interest to know why a large number of cells from 

 the blood should be present in milk, whether they have strayed 

 into the lumen of the gland and been thrown out in the process of 

 secretion, whether they can be regarded as denoting an abnormal 

 condition, or whether they should be regarded as providing 

 nutriment for the suckling animal. 



The sanitarian is mainly concerned to determine whether the 

 cells present in the milk are healthy or not. The origin of the 

 cells is important to him, because if they should be shown to be 

 derived from the blood, when they are present in large quantities, 

 it might be supposed that they were of the nature of pus cells, that 

 is, that they were dead leucocytes which had been killed in the 

 attempt to resist bacterial infection in the gland. 



It must be admitted that at the present time opinions are not 

 agreed upon this question. There is no means of distinguishing 

 satisfactorily between dead and living leucocytes. Moreover, the 

 cells of the mammary gland, of which a number undoubtedly 

 would occur in milk, resemble very closely certain varieties of 

 leucocytes. It is impossible here to consider at any length the 

 structure of the different cells which are present in milk, but the 

 main classes into which they can be placed may be mentioned. 

 There would appear to be general agreement as to the presence of 

 three main classes of cells : (i) Large uninucleated cells, (2) multi- 

 nucleated cells, (3) small uninucleated cells. These are present 

 in different proportions in different samples of milk examined. 

 Pictures of the cells in these three classes are shown in the plate 

 facing p. 136. In addition a considerable number of other cells 

 occur, but in small numbers. 



Great differences of opinion appear to arise round the second 

 class of cells, namely, the multinucleated. Some observers 1 



1 Cp. Winkler and Hewlett. 



