49 2 Brown. — Studies in the Physiology of Parasitism . IV. 
By applying the method described on p. 488, it is possible to determine 
the factor responsible for the reduced activities of the H preparations 
tabulated on p. 489. The table gives the enzymic activities of the various 
preparations indicated. 
H 7 , H 14 , H 21 are, as before, the preparations obtained by extracting hyphal material of 7, 14, 21 
days’ age respectively ; H/, H u ', H 21 ' are the corresponding deactivated extracts. 
S = Standard extract. 
S = 1 H 7 = 02 H j4 = 0'03-0-04 H 21 < 0*02 
SS' = o*8 Ht-S 7 = cri6 H 14 S / = 004 H 2 iS a •< 0*02 
.S'S = o*8 H/S = o-8 H 14 'S = o-8 H 21 'S = o-S 
The reduction of activity of S'S, H/S, H 14 'S, and H 2 /S, as compared 
with S, is about equal to that produced by dilution of S with an equal 
volume of distilled water. It is therefore plain that S, H 7 , H 14 , H 21 all 
contain amounts of retarding substances too small to be recognized by the 
method. The weakness of the preparation H 7 S' as compared with H/S 
shows that the small activity of the H 7 preparation is due simply to the 
small concentration in it of the enzyme ; and this is true a fortiori in the 
case of the H 14 and H 21 preparations. 
Spores sown thickly. Spores were sown on circular glass plates in the 
ratio of o»i c.c. of spores to 10 c.c. turnip extract. The following table 
gives the data obtained as to yield of mycelium and activity of the 
corresponding H preparations : 
Stage of Germination. 
Ungerminated 
8 hrs. germination 
1 day’s ,, 
2 days’ ,, 
Yietd per Plate ( dry wt.). Notation. 
0*01 
grin. 
H 0 
0*02 
>> 
H. 
o-i 4 
99 
0-17 
99 
h 2 
0'i6 
„ 
h 4 
0.14 
99 
He 
Activity. 
0*1 grm. m 
o*i grm. in 
o*i grm. 
1-5 c.c. 
3 c.c. 
in 4*5 c.c. 
0.1 
— 
— 
0-19 
°*75 
0-12 
o*6 
1 
o-75 
0-6 
o*75 
o-5 
0-38 
0-25 
— 
o*i 7 
The features brought out by the above table are : 
1. The yield of dry material for a given quantity of spores sown 
reaches a maximum in the neighbourhood of the second day. Subsequently 
a slow decrease in dry weight takes place. This decrease is probably to be 
ascribed to respiration. 
2 . The activity of the extract obtainable from the dried mycelium 
reaches a maximum about the first or second day ; on the fourth day it is 
distinctly, and on the sixth day very considerably, reduced. 
In the above table, extraction was made on the basis of equal 
quantities of dry material. By combining the curves of activity and of 
yield, it is readily seen that when extraction is made on the basis of equal 
