1919] 



Boeck: Studies on Giardia Microti 



99 



be followed by a cycle when the number of cysts reached nine for 

 three successive days. The cysts had disappeared from the faeces 

 when the last examination was made. The intervals between the 

 modes one, two, three, and four are 8%? 5, and 6 days, respectively. 



Rat 13. The infection of the rat was light, for the number of 

 cysts was small and there were only two cycles of encystment during 

 the twenty-eight days. The first period when the cysts were in the 

 faeces extended from November 1 to 5, with the highest number of 



25 26 27 28 29 30' 31 1 



10 11 12 13 14 15 16 17 18 19 20 21 



3 4 5 6 7 8 9 



Rat 14 

 Fig. 13 



cysts coming on November 3 and 4; then for a day no cysts were 

 found. The next period of cysts in the faeces was from November 

 7 to 10. In this period there was one day, November 8, when no 

 cysts were found; but since the number of cysts found in the other 

 days was very small it is probable cysts were present on November 8 

 and escaped detection because of their small numbers. The mode 

 of this second period was reached on November 9 when five cysts were 

 counted in twenty fields. The interval between the two modes is six 

 days in each case. 



Rat 14. The infection in this rat was the heaviest for all the rats 

 examined. The maximum numbers of cysts detected ran higher than 



