afternoon. The North Wall sample was i^acked in ice and 

 dealt with the following morning, November 4th. The usual 

 procedure was followed, viz. : an emulsion of five mussels in 

 250 c.c. of sterile water, giving a proportion of one mussel in 

 50 c.c, or one-fiftieth of a mussel in 1 c.c. was made. One 

 c.c. of this diluted emulsion was plated in MacConkey's Bile 

 Salt Neutral-red Lactose Agar, live plates being made, and 

 these were incubated at 37 C. for 24 hours. In addition, four 

 tubes of Bile Salt lactose litmus broth were inoculated as 

 follows. From the original emulsion of five mussels in 250 c.c. 

 of sterile water, 1 c.c. was taken and put into 100 c.c. of sterile 

 M'ater. This was called Dilution I., and each c.c. contained the 

 equivalent of ^^th part of a mussel. 



From Dilution I., 1 c.c. was taken and put into another 

 100 c.c. of sterile water. This was called Dilution II., and 

 each c.c. contained r;^5;^th part of a mussel. 



From Dilution II, 1 c.c. was taken and put into 100 c.c. 

 of sterile water and called dilution III., and each c.c. contained 

 5^:i55otfi part of a mussel. 



From Dilution III., 1 c.c. was taken and put into 100 c.c. 

 of sterile water and called Dilution IV., and each c.c. contained 

 6":5Ssi5:o'5"oth part of a mussel. 



Thus, four dilutions were made, each succeeding one 

 being 100 times more dilute than its predecessor. From each 

 Dilution I., II., III. and IV., 10 c.c. were taken and put into 

 four tubes respectively of Bile Salt, lactose, litmus broth 

 and incubated at 37^ C. Thus it Avill be seen that the quantity 

 of mussel in each tube was ,-;^|,th in I., .;;5;^th in II., s.oon.ooo ^^"^ i^"^ 

 III., and 500,0^,000^^ ill IV. 



It is not considered necessary to give details of sterilisa- 

 tion, except that all the usual precautions were observed. 

 After 24 and 48 hours" incubation at 37° C, the plates Mere 

 counted, with the follo\A ing results : — 



