556 Riba Dr. KE. W. A. Walker.. ' [Feb. 18, 
probable, that the causal agent of strangles is an independent and specific 
organism; but this would only prove that Marmorek was correct in his 
conclusions as regards the streptococci, and that this organism is not a true 
streptococcus at all, in the usual sense, any more than is the Streptococcus 
lanceolatus of pneumonia. 
Jensen makes the suggestion that when a single streptococcal form (like 
strangles) shows so great a constancy in the test media, it is the most 
probable conclusion that other streptococci also possess constant reactions. 
It may be pointed out that a generalisation of this character from a single 
instance is extremely apt to be fallacious. But a consideration of the facts 
adduced, namely, that on the one hand strangles presents different patho- 
logical events, the organisms being identical to the test media, while on the 
other hand similar conditions of disease may be occasioned by streptococci 
which give quite different series of reactions in these media, suggests that the 
reactions of true streptococci possess no fundamental relation to their 
pathogenicity, and present no evidence of permanence. _ 
Although the test media have been shown to afford no evidence of the 
diversity of human streptococci, it is still possible that they may be made to 
serve a useful purpose in supplying indications as to the probable recent or 
habitual environment of particular strains. 
A study of the very numerous and careful observations made by other 
workers and notably by Gordon, Houston, and Andrewes and Horder, 
suggests that on continued residence ina fairly uniform environment, as for 
example in the human mouth, the streptococcus tends to assume a moderately 
uniform series of reactions. But there is no satisfactory evidence as to the 
length of time such a process may require. 
From early in 1908 our laboratory media have been prepared in a fairly 
uniform manner save for the natural variations in “meat extract.” And it 
might be thought from an inspection of Table III above that the streptococci 
cultivated in stab agar were actually tending to a definite series of reactions 
such as that exhibited in 1910 by L, P, and V, and almost reached by 8, M, 
and H, G for the time remaining refractory. 
Again in Table V it is very striking how after eight weeks in inulin 
medium L, §, and G reach an identity which M falls short of only in the 
matter of clotting milk, while P appears to be moving slowly in the same 
direction. On returning to stab agar for three months Land P re-assume 
and S now assumes the reactions seen before from agar cultures. 
This evidence, however, does not amount to more than a suggestion of what 
might prove to be the fact upon an extended trial and the use of suitably 
selected media. | 
