
160 REPORT OF THE DIRECTOR OF THE 
CHANGES IN Minx GiopuLtes Durinc LAcTATION. 
It is well known that the average size of the milk globules 
diminishes during the progress of lactation, also that the yield of 
milk decreases in volume, also that the number of milk globules 
in a given volume of milk increases as lactation advances. 
It is an interesting question in its physiological bearings and of 
great practical value to determine whether the actual number of 
fat globules secreted by the cow increases during the moaths 
of lactation. 
Our records show an aggregate of 489 actual counts of samples 
of milk from fifteen cows and extending through an average of 
fourteen months lactation and the number of globules actually 
present in a given volume (.0001 c. m. m.) was determined in each 
case. 
We have also the daily yield of milk of these cows during the 
same period. By dividing the period of lactation of each cow 
into four equal periods, we find upon an average that the milk 
yield for these periods given in percentages was as follows: 
First period 100; second period 95; third period 76.2; fourth 
period 70.6. In a similar way we find that the number of fat 
globules in a definite volume of milk varied as follows: | 
First period 100; second period 144; third period 195; fourth 
period 267. : 
If now we combine these proportions we have the following as 
representing the actual number of globules of fat secreted, with- 
out regard to the milk yield, viz.: First period 100; second 
period 137; third period 149; fourth period 189. 
It appears therefore that there is a rather steady increase in the 
number of fat globules secreted, and that upon an average there 
are eighty-nine per cent more present in the milk during the 
last than during the first quarter. ) 
It would be interesting to know whether this increase is due to 
an increased development of the fat producing or seereting cells, 
a supposition not improbable in consideration of this being the 
first period of lactation with these animals; or may it be due to 
the breaking up of the larger fat globules, a very impropable 
supposition, although such breaking up would increase the num- 
ber and decrease the size, both well known phenomena ; or may it 

