134 Physiologie der Zellen, Gewebe und Organe. 



the Chinese Cling group are the most slowly started into growth in early winter 

 and bloom as late as any of the varieties. Killing of apple buds from low tem- 

 peratures is not common but has been observed. The blossoms and young fruit 

 of the apple will not generally withstand as low temperature as will the blos- 

 soms or young fruit of equal age of the peach. While the killing of cherry and 

 plum buds is less common than the killing of buds of the peach, such killing is 

 often to be observed in some sections. 



There is a review of the literature on the subject of freezing of plant 

 tissue. Pearl. 



336) Breed, K. S., Cells in Milk Derived from the Udder. In: N. Y. Agr. 

 Espt. Sta. Bull. No. 380, S. 139—200, Mar. 1914. 



The results reported in this paper confirm the conclusions formulated by 

 Breed and Stiger in an earlier paper and give niore definite Statements in re- 

 gard to some points. 



Apparently the largest average number of the cells present in milk occurs 

 in colostral milk but equally large numbers of cells occasionally occur in milk 

 drawn at any portion of the lactation period. Several very high cell counts have 

 been obtained from milk of animals nearing the end of their lactation periods 

 and the evidence here given indicates that such high counts are more common 

 during the latter part of the lactation period than during the height of lac- 

 tation, but the average cell counts for the latter part of the lactation period 

 do not seem to be markedly higher than the average cell counts of earlier 

 parts of the period. There are marked daily variations in the number of 

 cells discharged which do not show a close correlation with any of the 

 suggested causes for such variations. No constant relation between the 

 number of cells discharged in the foremilk and the number discharged in the 

 milking process has been found. It is clear that there is an increase in the 

 number of cells in the Strippings which may possibly be due to manipulation of 

 the udder as suggested by other investigators. However, it is equally possible 

 that this increase may be due to other factors. The four quarters of the udder 

 are practically independent of each other, so far as the discharge of the cells 

 is concerned, indicating that the principal cause of the. discharge is something 

 which affects the quarters separately rather than the udder as a whole. Changes 

 of a considerable amount in the vacuum used to operate cow milkers were found 

 to be entirely without effect on the cell content of the milk. Several things 

 seem to indicate that the number of cells present in milk drawn by the type of 

 machines here used is somewhat less than that of hand-drawn milk. The rea- 

 sons for the discharge of the two kinds of cellular elements are undoubtedly 

 entirely different. The epithelial cells are presumably discharged because they 

 are worn out in the process of the secretion of the milk. The reason or rea- 

 sons for the presence of the leucocytes are not so clear. Enough data were se- 

 cured however to make it probable that there are other reasons for the discharge 

 of leucocytes in the milk than the presence of bacteria in the udder. These other 

 reasons undoubtedly have to do with the physiological conditions surrounding the 

 process of milk secretion. No differential counting of these cells has ever been 

 attempted where a satisfactory technique has been used. It is therefore not sur- 

 prising that the real reasons for the discharge of the two kinds of cells are so 

 obscure. It is not at all probable that the ratio between the numbers of the 

 two kinds of cells remains constant during the entire lactation period. It re- 

 mains for future investigation to show what these fluctuations are and to find 

 the cause or causes of them. Pearl. 



